Daughter won't go to dad's anymore

She's 14 and just told me she doesn't want to stay at her dad's house every other weekend. Says she wants to hang out with friends and do her own thing. Her dad is devastated about this. I know she's growing up but I also don't want to push her to do something she doesn't want to do. He's threatening legal action saying I've turned her against him but that's not fair. What do I do here?