Based on the size of your DD, I would definitely recommend moving up to a 32. I know kids often like to stay with what they're familiar with, but if it's costing them performance, it's not the best choice. Try to get to pay attention to the improvement in results, if you can, and maybe that will help.
The idea of new tape is a good plan for a hand-me-down.
^^^ This
Get her into a 32" and around 22 ounces.