I think she is now. When she was introduced she wasn't, but I think they have aged her up as they tend to do with female superheroes that become popular.
Didn't the recent stuff with young Cyclops confirm that she is still young though? I don't keep up with much Marvel stuff anymore, but some friends were saying they were surprised how young she still was.
Maybe they were just insinuating her age to past Cyclops' age, which I don't know either, although I think I've been told they're all in their teens.