Your wife is a polysubstance addict and it sounds like instead of taking the opportunity that rehab is, she chose instead, to focus on someone she met, there.
People who feel like crap about themselves seem to often have the need to put down others so they can sustain a fantasy of superiority. Reality is, this says all that can be said about your wife and her side kick, than it does anything about your and your children.
Like the others have said, it's time to focus on learning how stop focusing on her and her problems and put your time and attention back on yourself and your children.