Ball pythons are better measured by weight because it's hard to get them to stretch out.
An adult female is usually 2,000-3,000 grams. Sometimes more.
The shed is stretchy and not a good indication of length.
I think the hide size is fine as long as she is using it. They often like to wear them as hats.
You can upgrade to a larger size if you want but not required.
Sent from my iPhone using Tapatalk