There's a line between presenting a good picture, and lying.
Wearing flattering clothing and makeup, using good lighting and a good angle for the photo, and so on are fair game. Odds are you're going to wear flattering clothing and makeup when you go on a date as well, even if you normally like more casual clothes.
Photoshopping out temporary defects (a zit, for example) or removing red-eye is also fine. Smoothing out temporary bags from under the eyes is not too bad either.
But photoshopping out five pounds, yellow teeth and permanent under-eye bags goes over that line, unless the subject is going to lose five pounds, get a teeth whitening, and get rid of the under eye bags before she goes on a first date. It can backfire, when she goes on a date and the guy looks at her, gets this disappointed look on his face, and makes an excuse to leave. Better to not have him reply at all, even if it means you don't get as many responses.