From all of the posts and advice I've read here I think that would be called "CakeEating". The fact that she gets that "friend" time with you when she wants, and she can buck her responsibility with the dogs when it suits her because you'll pick up her slack.
I'm sure the recommendation would be "cut the rope", but I'm not sure if I would be able to if the same thing happened to me. Also, it would be tougher for her to see your changes and thus believe you've really changed.
I think the best thing to do would be to find a way to maintain the friendship but not allow her to buck her responsibilities.
If she was to take 1 or 2 of the dogs, would she still feel obligated or inclined to come over on occasion to see or walk the dog(s) that are your responsibility?
Just a thought.
Me - 34 W - 33 M - 8 years T - 15 years D7, D5, D2 Bomb Nov 10/2010 "I'm not happy and INILWY" W Staying for the kids Mar 13/2011