It's a snappy and somewhat American way of saying that she got her man. They met at the rehabilitation clinic, each of them there for different things. She stopped being an addict, got bigger and somehow - you know how women can - got the bloke called Forrest as well when she left the rehab. place. He was part of her changed life - her 'deal'.
That is how I read it, anyway! I hope you get some more confirmations/views.
