Sorry 'bout the pity parade that storms into your life every now and again.
I think your mom needs to grow up a bit, a little better judgment and self-reliance never hurt nobody.
Of course, maybe she doesn't want to change. Maybe she just likes a certain part of that man and loves it until another part of him shows up - and then she takes a break from him via break-up-depression-cheerup and goes through the whole cycle again. ..........if that's what she prefers, I would suggest for her to get a journal....... or a facebook account....... or a myspace...... so she'd have another's shoulder to go cry on. Depending on one's child shows a lack of parental-strength / responsibility / maturity.
.......... but then again, that's just me being assuming and analyzing.
... so yeah, ignore that. Hope she gets better so she can get out of your hair!