I don't think she's slow at all! I think she's pretty normal, personally... I always get a bit frustrated and worried myself at the beginning of a grow. You KNOW that these plants are supposed to grow quickly (and they do!) but the first few days - even the first couple of weeks seems to take them so long to get "big." But then the explosion happens.... My Pinky was like that - seemed to be stuck at a certain height, not growing very much - and then all of a sudden, she started growing 1.5" every day! So be patient, she looks VERY strong, VERY healthy and she's going to be absolutely great.
Good luck!