My daughter was the second shortest girl on her team last year and she based, so don't use your height as an excuse. Honestly at this point in the season, your stunts should be a little hard. This is still the learning part of the year. Are you lifting with your legs or are you trying to use your arms as your main leverage? Your strength should come from your legs and your core, so if they aren't strong start conditioning them.
Have you asked your coach for tips? Ask for help and be open to the advice.
If there are specific things that you're having problems with, post them here and I'm sure that you'll get great advice. Whether you follow it, though, is up to you.