Michelle got carried away with her feelings for Danny and naively thought they would solve everything, but as Meta basically pointed out, love or whatever Michelle is feeling for Danny is not the answer to everything. In a marriage, you can't only love the good part, in this case, the gentleman Danny who's well-spoken and well-mannered, the Danny who loves his grandmother, the Danny who's nice to children and little dogs and cats, the Danny (most of all) who worships the ground she walks on. No. It would be lovely, but you can't. There's more to Danny than just this nice side.
He was groomed to be ruthless, and that's part of the deal Michelle has to face if she's going to stay in this marriage. She wouldn't face it consciously, so her subsconscious took over, and it was something she clearly wasn't ready to deal with at this point. I don't believe she fears Danny himself. I never have. Not because I don't want to, but because I haven't seen the signs. (And believe me, I am alert to those signs, I'm not blind in my devotion to Manny.) I believe that what Michelle fears is what comes with Danny, for example a family code that just doesn't make any sense to her but to which Danny has pledged loyalty.
One last thing I'd like to address is that I don't think Danny has violent tendencies. Mick has/had violent tendencies, not Danny. Danny, to put it crudely, is a control freak. He keeps a very tight rein on his emotions and reflexes, he doesn't act on provocation easily. He sometimes strikes me as a soldier, or a monk, in how disciplined he is and how he always keeps his deepest thoughts and emotions to himself. Until Michelle came along.
She wreaked havoc on his life, and that's why he's spinning out of control. The life he wanted with Michelle is gone, and the life he's trying to go back to is no longer there either because of the changes Michelle has wrought in himself. What you view as violent tendencies (which bespeak an habitude), I see them as something unusual with Danny, something that Michelle has caused (I'm not blaming her, I'm just talking in the cause-and-effect sense), and something that Danny (as a man who values self-control above everything else) himself doesn't like.
kristi