Hmm... yeah, Midori is a little bitchy about everything, but she's used to being treated like a monster, so that's just how she protects herself. She just needs to eat some pickles and chill a bit. Ran will fix it all, once she picks up all of the various giant clueweights dropped all over the place.
Personally, I don't mind the odd slap or nasty comment. Makes the show less bland and more interesting. I like Midori the way she is. Then again, I like Ueda Kana's voice either way. All we need now is a なんでやねん? and we're good to go.
But as someone who has watched MSGM, it's weird hearing Yumi's voice coming from a middle-school Sachiko wannabe's body.