Hi M.,
I know how hard it can be with 13-year-olds complaining about where they want to live. We have one who lives with her mother and her stepdad and is constantly complaining about it.
She tells us she wants to live with us and tells her mother she wants to live with us or with Steve (her deceased grandmother's fiancee, with whom she lived until she was 9). It upsets her mother to no end; she gets upset and blames it on us, when we don't do anything different with her than with the other three. It makes it tough on everyone.
If your parents are telling your child she can come live there, they are absolutely going to have to stop it. Like the other moms said, that is YOUR child and you will be the one to decide that. While having your child live with your parents won't mean you're a bad mother, it should not be the first tested solution. Like I said before, my oldest lived with her grandmother until she was nine. At first it was because my husband and her mother were too young and inexperienced to be properly raising a child; then, her grandmother had their guardianship removed because she just didn't want her back with either of her parents. She didn't want to adopt her, but she didn't want to give up her monthly stipend check either. After her dad and I moved in together when she was six, Gina used to tell her grandma she wanted to move in with us. Grandma retaliated by cutting off our visitation without an explanation. It was extremely hard on everyone when she got terminal cancer, too, because Gina still had to live there through the bitter end; our court battle was unsuccessful, and it left my daughter with mental problems. Grandma (Mom's mom) told her every day for a year, "I'll be so proud of you when you make the right choice to live with Mommy," so when Grandma died, Gina, of course, chose to live with Mommy. That was four years ago, and as you can see she is still miserable there.
You need to have a talk with your daughter too to find out why she is thinking of leaving your family to live with her grandparents. It may be she never thought of the idea until they mentioned it, and now she's using it to hurt/upset you and her stepdad. It may be that she feels left out because you have the little ones to care for, and you need to make more time for you and her to share one-on-one time together. It may be that she's jealous that your little ones have their father while she doesn't have hers, and you may all need to attend some family therapy sessions together to help her and her stepdad bond (trust me, it can be done; my oldest two aren't biologically mine, but I have loved them and cared for them as my own for the past eight years). Whatever it is, the best bet is to try and work it out before you even think about letting her live with her grandparents, because as I mentioned, it may not be the easiest thing in the world to get her back into your home later.
If you are depressed, I advise you to seek individual counseling. While I don't always feel medication is the best course of action, if it is a legitimate imbalance of biochemicals in your brain meds can help. Counseling should also help.
I would say, too, that the overnight and weekend visits should be temporarily halted, at least until you are able to talk to her and your parents (separately) and hopefully work these issues out. At 13 if it is a childcare issue (especially during the summer) see if you can enlist the help of her best friend's mom in the matter. I can remember at 13 spending many an overnight at friends' houses when I wasn't getting along too well with my parents; perhaps you can work it out so the overnight visits are with her friend/s instead of your parents.
Good luck, and I hope everything works out well for you.
--M.