I'm a man, 57, living with my girlfriend, 53, for 7 years now. She has a 19 year old daughter living with us, who is attending college and doing very well. Probably when her daughter was 14 or so, my girlfriend seemed to become critical of her daughter, her grades weren't good enough, she was lazy, etc. Her daughter seemed to be just a normal teenager to me, actually her grades were pretty good (3.0) and she never got into any trouble. And we did a lot of stuff together as a family. As her daughter got older, her grades improved, and she graduated with a 3.6 average. I'm proud of her myself. My girlfriend had back surgery 2 years ago, and told her daughter she would have to take over household chores while she recovered. But she is sore a lot, and so her daughter still does the laundry, cleans the house, does the dishes and most of the cooking. Never well enough for my girlfriend though. I don't hear any positive reinforcement from her anymore. I try to encourage her daughter, I've become like a dad to her, but I know it's building resentment in her. I've tried to suggest therapy to her daughter, her mom is in it already. What can I do? Why is this happening?