I don't think she can get out of cosigning the lease. The whole point of her cosigning is that the first girl was not credit worthy, so the 2nd girl signed up to guarantee her. People are pretty dumb when it comes to doing stuff like this for their friends.
I have a friend who is in a somewhat similar situation. Her friend from way back moved back into town and was crashing on people's couches. He has no job, and isn't the kind of guy who has a lot of employment prospects. Her roommate was moving out at the time and she had new people with jobs inquiring about the free room. When she told me she was giving the room to her jobless friend I warned her that she should consider the fact that he might not be able to pay. She said she knew it was possible and wasn't worried. Fast forward to 3 months later she is now trying to kick him out because he still has no job and hasn't paid a dime in rent. She's had to pay all of it herself. I really want to tell her "I told you so" but that wouldn't accomplish anything. I only hope she will learn from this and never make such a mistake again.
OP, all the girl can do is accept the consequences.