Sometimes "indifference" hurts as badly as malice.

Ok, first off, I'd like to point out that I could never compare what's going on in my life to that of others' lives. So please listen to what I have to say, rather than picking at my title. Also, I'm on my mobile, so sorry for any formatting issues.My SO's mother is a very... unpleasant woman, shall we say. She's also highly judgmental of me and may lash out at me, through my SO (she notches to him and he's forced to listen, which just stresses him out), with no warning. That being said, she has no idea that I'm bi, and if she were to find out, she would likely start calling me a whore/promiscuous/etc.I really have no intention of her finding out any time soon, since we still have to deal with her until we get a bit more financially stable. However, I'm worried about it slipping out somehow, since I'm out to just about everyone else that I know.What scares me the most, though, is less having to deal with her, and more that my dad is "indifferent" concerning my orientation, and would likely end up asking me why I would tell her--as if it would be my fault that she'd react that way. Essentially, I'm worried about victim blaming from my dad, who we also have to deal with until we're more financially stable. Tips/advice/stories/anecdotes? I'm cool with jokes, too. I'm feeling pretty down about this situation, so they'd probably cheer me up quite a bit.TL;DR: I'm bi, my SO's mom is crazy, and my dad is the type of indifferent person where he's not actually indifferent, but prefers to not talk about it. If my SO's mom finds out I'm bi, dad will essentially be on her side.Edit: clarification