Character mistake: When Kay convinces Charity to switch costumes for the Halloween Dance, Kay mistakenly calls Charity "Kay."
Factual error: When Jessica and Miguel finally convince Charity to play a videogame, they start playing, but you can see that there is no cartridge in the Nintendo 64 (which cannot play a game without the cartridge being inserted).
Answer: I don't know about good not wanting them to be together, but I know the evil side doesn't want them together because once they sleep together, then Charity's powers will multiply, and she will be a driving force against the evil darkside.