@cumdumpster1 What is wrong with slang? Slang and accents are the one thing that is consistent across languages, shortenings, misreading or hearings of words, combining words, and even entirely new words, they are all considered "slang" until they enter the official lexicon of the language, and as long as the manga is readable, you should have no problem with it, they are doing this for free, you know, so even if they speak like "retards with broken english", you shouldn't really complain about it, its a choice the translators make, heck, it could make it more faithful to the original japanese. Yes, you can and should give constructive criticism, but meaningless insults and derogatory terms aren't really going to get anything done. But its your opinion and way of speaking, so who am I to tell you to change.
Also, realistically, body in charge is probably fine, parallel wills all stem from the skill that spider-chan has, so in the event of being "cut off" from her host form and like dying or something, it would make sense that the skill reforms the parallel will, or the skill regresses a level or something, also, in the event mother dies, it'll probably just be signified by her mental self either vanishing or fading away, and in the process, her mental block will probably be lifted, giving body in charge a chance to escape before she like hits the ground or something.