@KuroAnsatsu We don't know that for sure yet. She said she thought she could support him because he never was physical. But that was her state of mind before he started taking it out on her daughter. We still don't know what he did to Mayu; it could be just about anything.
@GodGinrai and @KuroAnsatsu Actually, back when she was talking with Yuki about protecting Mayu she did say that he didn't need to worry so much because the stepdad(?) wasn't the kind of person that'd resort to violence - don't remember the exact chapter though.