Let's see, orphan kid gets shifted around from home to home. Clearly there are going to be issues of attachment. Typical of such children is that they are really really well behaved at first, sometimes for quite a while; but after some time they will start to test the situation to see if these new parents can be trusted. Whoops, Bette flunks adoptive parenting 101. Clearly her love comes with conditions—exactly the situation Micah would be testing. Through her actions Bette is saying, if you play the violin (payment), I'll love you and take care of you (reward), if not, I'll throw you to the wolves. This is a story, so there will probably be a happy ending; and, of course, the author has set that up with David Stirling, when he comes back into the story later.
I am not so impressed with Megan as others seem to be. She seems to work from the premise that Micah's inability to toe the line set by Bette and society is Micah's fault—more love with conditions. Frankly, of all the women who are oppressing Micah, I like the girlfriend best, drugs and all.
Lastly, I'll add that I am kind of furious with Bette, she has stolen Micah's music, which started as a loving communion with his father, Poppa M, and then an expression of grief at Poppa M's death and the loss of his home, and she has redirected his motivation into a professional ambitions whose goal seems to be competition, fame, prestige, and perhaps money, but certainly not love of music. I am a musician myself, and what seems to be missing from Micah's musical development is not the need for more practice—lot's of really good musicians don't actually practice all that much—but the delight one finds, not in the ego strokes of being a soloist, but in joining one's creativity with that of other musicians. In real life, I would expect a huge part of Micah and Bette's relationship would revolve around playing together, after all, we are told that Bette is a pianist of some ability and that all the children in her family have been taught, as well. Couple that with the fact that almost all of the violin repetoire requires either an orchestra, a keyboard player, or other string players and you can see that there is a strange lack of understanding in this story of what it means to be a musician. It is really only keyboard players and maybe guitarists who can develop their art as a sophisticated form of masturbation.