To add on to CT's point, I like to think that she realized she was much safer with Littlefoot and the others. I mean, despite her comment after their second encounter with Sharptooth ("Nobody is safe with you"), throughout the movie she really wasn't in so much danger while she was with them. Everytime she was alone, she was in some form of peril (when she found Sharptooth in the canyon and when she was running from the head-butters). She probably realized that considering how she was still alive because she was with the group, she really couldn't go off by herself, and she could especially not lead the group like Littlefoot did.