I don't spend much time thinking about glasses one way or another. Sometimes, they make the girl look cuter, sometimes they have the opposite effect. It all comes down to whether they suit her face. Just ask one or two of your not-fashion-clueless guy friends to go to the store with you and help you pick out a pair.
If women wear really stylishly looking glasses, where the frame is more expensive than the lenses and they really try to make a huge effort to stand out or make themselves look more attractive than they are.. that is a turn off. Glasses are meant to see better that's all they should be about.