Gefen, she could just say that there are different standards of tznius.
WIY, writersoul, and Syag, the question isn’t necessarily about halachic standards, it’s about the caller’s (or the boy’s) standards. If there’s a chance that his standards are sub-halachic, it still might be a good shidduch.
AFAIK, there’s no issur of lifnei iver for the one giving information if the girl dresses according to the boys’ standards, even if they’re not l’halachah.