daniela-
if you are giving your dd tylenol, that should help her with the teething pain. so i don't think that her naps are short due to teething, although they like to keep us guessing, so who knows?! :roll:
do you think that your dd is in need of increasing her awake time? around 6-7 months, my dd needed her awake time increased to about 2.5 hours. that really helped her naps start to get longer. has your dd recently reached a milestone like sitting up, crawling, etc? sometimes that throws off naps.
also, sometimes, my dd has a few days or a week of short naps for no apparent reason, then she will go back to long naps as if nothing happened. maybe if you have time, you can post your routine so we can be more specific.