It’s easy to change the name. Sometimes Thais even change their given name. But then you have to get many new documents:
Id-Card, housebook, passport, driving license, bank books, ownership of vehicles, …
If she has children: documents concerning the motherhood and for the school …
If she will ever inherit something in Thailand it might be a lot of paperwork or/and witnesses required to prove that she is really the legitimate heiress.