You should have, right then, said you were not okay with that.
Now its too late.
But, did your sister ASK you if it was okay... or did your sister just say... she is bringing her daughter along, and did not ask you?
If your Sister did not ask you if it was okay, then that is a bit presumptuous of your sister.
Or, maybe your sister does not equate this trip... with it being a "Moms only" type trip???? So she didn't bother to see her daughter coming along as a big deal.
(Is this your sister's only child? Or does she have more kids? If this is her only child, then sure she may feel bad leaving her behind).
BUT, you also need to tell your Sister, that you have NOT had any time away alone, since you had your 3 little kids, and its been EIGHT years... without any time off for yourself.
Your Sister... does not know that. It is not even on her radar.
So, she is not thinking about you in that sense. She only knows, "her" situation. Because you never told her your, situation.
You are not wrong.
She is not wrong.
BUT.... was it ever, stated between the two of you that this is a MOMS ONLY trip??? Because if not, then, anyone can go. Even your kids.
The thing is, siblings do not always know the full story nor can they read our minds. So if you are resentful about it, you better tell her.
If your sister is taking her 14 year old, yes it will change the dynamic of the trip. AND it may become a "Mommy/daughter" trip, instead of a Mom trip. So talk to your Sister. Right?