I am glad that it is settled at least for now. Be prepared for her to make another plea and for him to want to give in to it. She is clearly very manipulative and takes what advantage she can. So be sure to work at being a united front with him in regards to issues with the kids.
In fact, I would make it a rule that you must discuss major things like this with each other, WITHOUT the kid there OR waiting on the response on the phone or skype or whatever. Unless/until you have the time to discuss it without the pressure to give a response ASAP, no decision or agreement is to be made on issues like this. It is a good marriage rule, and esp a good parenting rule.
In addition, get a copy of Parenting your Teen with Love and Logic and both of you read it. You don't have her living with you, but you are still going to do some parneting and she may decide to come live with you at some point. This will help you be ready to handle things. Don't EVER agree to let ANYONE, especially one of your adult children, move in with-o a written lease agreement specifying conditions and terms including a move out date and rules and consequences for not following them, plus terms for eviction if rules are not followed. If you don't do this, you could end up having to go through a legal eviction process or even getting a restraining order if she is violent or abusive or brings drugs into your home. If you don't prepare ahead, you will pay bigtime later!