I agree with MomoTheStrange. The guy did her wrong and broke her heart. Allison wants to show the guy that she doesn't need him. She's basically stating that she can still breath and survive without him. That's he's no longer her everything. At first she didn't realize that she was letting herself go through such suffering but when she did in fact realize what was happening she stopped. She let him know, point blank, that she doesn't need him and things are better without him.
I agree with MomoTheStrange. The guy did her wrong and broke her heart. Allison wants to show the guy that she doesn't need him. She's basically stating that she can still breath and survive without him. That's he's no longer her everything. At first she didn't realize that she was letting herself go through such suffering but when she did in fact realize what was happening she stopped. She let him know, point blank, that she doesn't need him and things are better without him.