She won't be that bad, so long as you don't make any dumb decisions.
I mean, that's basically what romance means in there world. Trust me, the bad ends will not be the best option.
I for one love femdom and yandere's and to see Mei is both made my day ngl.
Given the world the MC lives in, assuming Mei is developing real romantic feelings for the MC, Mei is the best chance of a "happy ending" in the traditional sense. She shows concern for the MC's welbeing, improves your living conditions and has shown she is capable of defending the MC given her aptitude to magic. However if she is a yandere, then not reciprocating her feelings, not being loyal, and betraying her, will bring out the dangerous side of the yandere archetype and if other women try to "steal" you, she'll become more possessive to the MC, and aggressive to other women. I think she's a character who will have good or bad endings depending on yours choices and even the "choices" of other characters.
In short, I enjoy the yandere archtype, hope that's where Mei is going but I also understand it's not for everyone, so maybe there can be a girl who is more vanilla who will have a tamer happy/bad ending, such as Susan, she could also steal the MC from Akame. That would give the player an out if Akame is too intense for them as well.
Just my two cents.
Keep up the good work, I'm liking the game, it has potential.