My daughter wants to leave my house because she is unhappy and move in with her boyfriends family. Boyfriends mother knows and agrees. I dont think she wants to leave for any other reason than she loves her boyfriend. She says my chores are too strict and I stress her out about wanting good grades. I also believe if I force her to stay she will either run away (and i wont know where she is) or she will put all her anger into fighting with her brother and sister or me. I dont want her to hate me and I want her to have her freedom but I dont think she is old enough. Please help.
You simply say no. She can carry on and cry and stomp her feet all she wants. The answer will still be no.
However, if this were *my* daughter, I would also sit her down and explain to her why you do the things that you do.
She has chores because you all live together as a family, and you all share in the work around the house. Find out what it is about her chores that she doesn't like, and see if there are others that she might prefer to do instead. Nothing wrong with changing around who does what.
You want her to get good grades because that will provide her with the most opportunities for the future. The better her grades are, the more choices she will have - and it's especially important these days for a woman to have the ability to support herself and/or children.
That you appreciate her feelings for her young man, and understand them. But that you do not feel it is in her best interests to live with him at her age. That he is certainly welcome to come over often and spend time with her. But you simply cannot agree to to her moving in with his family. But if she finds living in YOUR home intolerable, then perhaps the you should talk to her Dad about living with him (reading between the lines, it would seem you don't live together?).
ETA: Has his Mom actually told YOU that she is fine with your daughter moving in? Or is that what your daughter telling you? If the latter, he's probably told his Mom that YOU are fine with his g/f moving in with them. Manipulation 101.