One of my bridesmaids was asked to stand up in another wedding. On the same day as mine. She was asked quite a long time after I asked her. I am struggling because I know how good of friends she is with the other bride. The bridesmaid keeps asking if she can do things with the other bride. The biggies so far have been to leave the reception to go to hers and today she asked if she can get her hair and makeup done with the party of the other bride. I don't know how to handle this. It doesn't help that she is not good at time management in the first place and I would be afraid that she'd be late for photos or other events. Should I let her go or put my foot down?
Edit: She is not planning on being in the other wedding, she is just asking to participate in the above mentioned events. I commented below as well.