Wouldn't your contract get cheaper if you'd kept your phone? I'm not in the US so I don't know how true that is there (the difference might be miniscule). And repairing Iphone-Displays is fairly easy, I'd do it for you, but I guess shipping would break the bank here. Well you can't think about it.

And btw: what your stepmother pulled is really a dick move and it was sure not not intentional. I don't know what her problem is but I wouldn't even pull that on people I don't particularly like. And maybe wait a few days and if she's still rubbing her new phone in your face you should talk to you das and explain it to I'm exactly like you did here.