The APTA offers guidance that foreign educated physical therapy professionals should follow that can be found here: https://www.apta.org/Licensure/ForeignEducated/68
Each state also offers its own set of regulations over physical therapy professionals. Texas provides information for foreign trained PT professionals on this page: https://www.ptot.texas.gov/page/foreign-trained-applicants78
One of the requirements will involve an English test and there are additional requirements as well as more details on each at the links above.
I hope this helps, good luck to your sister!