The tin[wo]man does have a heart

I'm not backing down from my previous statements about Ruth.  I don't like her, not then and not now. However, in her weaker, somewhat dying, days, she showed what appeared to be actually remorse for her past actions.  "'I'd like you to forgive me, but i don't expect you to.  Anyway, that's not the half of it, not even a small bit of it...The main thing is, I kept you and Tommy apart" (Ishiguro, 232).  Ruth was like a selfish older sister to Kathy for most of their lives.  Tommy was her toy.  Even if she didn't care about him much, even if she didn't want to play with him, she did NOT want Kathy having him.  For that reason, she would hold onto that toy no matter what, out of pure spite.  At least, though, in the end, Ruth acknowledges the fact that she had done wrong.  She admitted to having kept two people who clearly loved each other apart.  What I don't understand is why Tommy didn't dump her snotty butt long before that point so that he could be with Kathy instead!