Well, for a long time MJ was flighty in her "Let's go to the disco!" way that didn't seem to make her a "bad girl" by anyone's standards. It's been a while since I've read the 60s Romita era, but I could get the ESSENTIALS easily enough.
Pretty much since the marriage onward, it's been set that a lot of MJ's party girl behavior back then was a cover for (a) her pain over her parents' break-up and (b) knowing Peter Parker was Spider-Man. This might be some way of making her "deeper" than just a flirty ditz, but I don't see it as making her more "worthy" of Peter as if she was less worthy before.