Breastfeeding is draining on your body? I nursed my 3 1/2 year old while pregnant with baby #3 and I did not find it to be draining at all. In fact, it gave me an incentive to get MORE rest because pregnancy naturally makes women more tired. However, I did wean my toddler when my breasts become too sensitive during pregnancy. Every woman is different, but my reason for weaning was because nursing was becoming painful.
So, if you are sure you want to wean, first of all, you need to stop nursing during the night. Without a doubt, a 16 month old is not waking up during the night because she is hungry. Thirsty maybe but you can easily remedy that with a sippy cup (not a bottle) of water...no milk, no juice. Just plain water. The point of cutting out night time sessions is to make it undesirable for her to wake up in the first place. IF she knows she is getting something yummy like juice or milk, that is all the incentive she needs to wake up...and more frequently. Give her water, only water and that will eliminate her desire to wake up.
Once you have gotten rid of the night time nursing sessions (could take a week or two, maybe a few days if you are lucky), cut out the day time sessions, leaving the first session of the day and the last session of the day the last ones to go. The last session of the day, from my experience, was the hardest for my toddler to give up. Replace those day time sessions with sippy cups of juice, water, or milk, and a snack and/or activity. Start making your breasts hard for her to get at by not wearing a nursing bra and tops that are hard to lift up. Make excuses by saying, "Mommy's milk is sleeping now, let's get something else to drink (or eat)." You don't have to drag it out unless you want to but you don't want to go "cold turkey." That would be unfair to your daughter. She is too young to understand and for her breastfeeding brings her comfort and you need to help her find other ways to find comfort. Make new routines in the morning so she isn't getting to breastfeed. I hope this all helps you. It could take about a month before she is totally weaned and once you stop a session, do NOT allow her to have it back. Good luck.