Advice for mom:
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I was blessed and lucky to get actual training from Dr Becky Bailey on some of her theories and methods ("Conscious Discipline) when I was teaching at an "inner city" school and if you give it a chance it is amazing. Her methods are based on the latest in brain research, which sounds ridiculous at first, but it's not.
In the meantime... 2 things that popped into my head when I read your request...
First of all, if she is acting like this (especially only with you) it is a learned behavior. She would not act this way if she was getting nothing out of it. Think hard-- what happens when she has her meltdowns/power struggles?? Do you eventually always give in? (If so, she has learned to just keep at it until she finds your breaking point because no doesn't really mean no.) Do you SOMETIMES give in? (In which case she never really knows if you really mean no when you say it.) Do you yell at her and get mad when she acts this way? (In which case she is getting negative attention-- all children prefer positive attention but will eat up negative attention if it is offered. Don't feel guilty if this is the case-- we all get upset sometimes as parents and you need to learn from the past and learn to control your own behavior in order to change hers.) The key to getting her to stop her meltdowns is to STOP FEEDING THEM. Seriously-- while you have some distance right now and you're reading this, I bet you think I'm wrong and you aren't doing anything to feed her bad behavior, but you are or she would not be acting this way with you. You have to use Dr. Bailey's method of being a broken record. When she wants to go to the bathroom after being put to bed, first of all you need to get in the habit of having her go to the bathroom right before bed to rule out the fact that she may really need to go. Then, when she asks, you very calmly say, "You already went to the bathroom. You may not go again until morning. It is time for bed." She'll ask again, and you very calmly say the EXACT SAME THING in a monotone, calm voice. If your voice escalates, she won. If you yell at her, she won. If you say something different, you are giving her attention (and feeding into a power struggle) when she should be going to bed, which is what she wants and shouldn't be getting when it is time for bed. Dr Bailey said you need to practice this in the mirror to make sure you are not showing anger or emotion-- it should be said as matter of fact as "this flower is blue." You wouldn't get mad and say, "THIS FLOWER IS BLUE!!!!" so practice that matter of fact monotone tone of voice and use it to let your daughter know that you have said what you mean and mean what you said and you will not be changing your mind and giving in to her. It's really, really hard for your own emotions not to escalate while hers are, but you are the adult and need to be in control of your emotions. I guarantee this method will eventually work IF YOU STAY CONSISTENT and always use it. She will get mad that you keep saying the same thing, but it will sink in that you mean what you say and no amount of tantrum will change your mind, period.
The other thing that came to mind was something you can start right away (again, learned from Dr. Bailey's Conscious Discipline strategies) is that if she wants to have her way and make decisions, let her... here's how to do it in a way that you get what you want but she thinks she is calling the shots and making her own decisions... Every time you want her to do something, give her TWO CHOICES. But there is a VERY IMPORTANT catch... the 2 choices always need to equate to getting what YOU want done. Only give two choices, no more than two. And always make sure you can live with both choices because she will pick one and you have to be able to happily accept and allow her to follow through with the choice she picks. The example Dr Bailey first gave when I heard of this strategy sounded so ridiculous, and then I saw it in action with my students and was blown away that it works nearly every time without fail... She said, for example, if you are reading a story to a group of kids and one of them refuses to sit quietly, you can say, "Jack, you may sit quietly with your hands in your lap or you may sit quietly with your hands on the carpet" or something similar. Either choice equates to him sitting quietly but he thinks it was HIS decision because he got to decide where to put his hands. You tricked his brain into thinking he made a choice rather than you making him doing something he doesn't want to do. The hard part is thinking on your toes for 2 choices, but you will get better at it once you start doing it on a regular basis. Here are some examples based on your original post, but feel free to email me with other issues you have with her and I can give you more examples of choices to offer. And by the way, offer the 2 choices in the matter of fact, monotone, broken record tone of repeating the 2 choices calmly until she picks one and follows through.
If she wants to jump out the window to see here dad, "Jumping out of the window is not safe. I love you and don't want you to get hurt. I understand that you miss your dad and I want you to be able to communicate with him. Do you want to draw him a picture we can send in the mail, or do you want to send him an email?" (Or do you want to write him a letter or call him on the phone-- or whatever 2 options work for you)
I don't really see the problem with her asking for something to eat even if she has already had dinner and dessert, but if this is an issue for you, try to figure out what it really is that she is looking for if you don't think the issue really is hunger-- off the top of my head I think it's the attention she gets from you from the power struggle of trying to get you to say yes, or else the attention she gets from you while you stop doing what you are doing to get her a snack. If you are OK with her eating but are too busy to keep dropping everything to feed her, try "You may have a snack that you can get for yourself such as ___ , or you can wait until I am finish doing___ and I will get you a snack." If you just don't want her to have anything else to eat for the evening, then try "You know the rule that you can't eat again after dessert (or this close to bedtime or whatever the issue is), but you can have a few minutes of mommy time. Do you want me to color with you for 10 minutes or play one game of Go Fish?" If there is some other issue with this asking for food thing that I am missing, let me know and I'll give you a better scenario.
Bathroom at bedtime is easy. Be proactive and have her "try" to go to the bathroom before she gets tucked in. If she says she doesn't have to go right now, say, "Once you get tucked in, you will not be allowed to go until the morning. Do you want to try to go now or do you want to wait until morning?" That way, waiting until morning was HER decision, not yours. See how that works?!?! Cool, huh?? And when she gets to bed and asks to go, make it a non-issue and ignore it by changing the subject. When she asks to go to the bathroom, remind her once and only once that she either just went or decided to wait until morning, then say, "So now it's time to stay in bed. Do you want your door open or closed?" (...or do you want the hall light on or off? ... or do you want the red blanket tonight or the blue one?... or do you want to sleep with your bear or your elephant?... or any other 2 choices that basically do not change the fact that she will be going to bed NOW and staying in her bedroom, but give her the freedom and power to make one last decision before the day is over. It doesn't effect your life in any way yet gives her this amazing sense of power that she made a decision as opposed to mommy always telling her what she can and can't do.
Please let me know if this is helpful to you and if it works. Once you get the hang of the 2 choice system, you will be blown away with how few power struggles you have with her. Another easy one to think of on your toes is when you want her to do something and she doesn't want to do it, say, "Do you want to do___ yourself or do you want me to help you?" Don't say it in a threatening way as though if she doesn't get it done that you are going to MAKE her do it-- instead, she will either accept doing it herself because it makes her feel like she is in control or she will accept your help because she really just wanted your attention-- either way, the task gets done so it's win-win!!