LuLu, stand your ground. Its great yo have everyone else she could ask on side also. She needs a swift kick in the butt & I think this is the way to do it.
She thinkins she can push you & win. Let her see she has another thing coming. Poopy, Nan & S and anyone else she thought she could fall back on & ask for money needs to be on your side 100% & sounds as though they are.

I know it woul dbe hard seeingher miss out on her formal but save all the sparkly things for her wedding when she is a mature women. At the moment she just sounds like a spoilt brat.
If she gets what she wants with this I think you have lost the battle for good.

Let her hate you & everyone else & think the world hates her etc, everything she can throw at you but remember when she is a little more grown up she should be better for it.
Don't give in .

Marlene - Blah I hope your DD see's some sence soon & realises you are not the evil selfish mother she thinks or makes you out to be. it sounds to me that the BF's parents need to stand their ground & kick her out LOL. Is she paying any kind of rent or board? I would be asking that they don't let her freeload.

I hope you can both sort out these girls. Im not looking forward to Isla hitting this age!