Hi Jamie,
I'm sorry for your Mom's troubles.
The surgeon who did the Whipple procedure told me that even with complete removal of the tumor from the pancreas, it is possible for the cancer to return. Statistically, the chances of recurrence are significant.
If there is any doubt they were unable to get all of the tumor removed, typically they will refer to an oncologist for follow up treatment. Usually radiation and / or chemotherapy depending on the patients specific circumstances.
I believe a diagnosis of pancreatic cancer will prevent any consideration of liver transplant. There are too few organ donations, with long waiting lists, so they select the patients most likely to have the longer term benefit of the transplant. If may be possible for cancer patients to receive transplants in other countries, but to my knowledge, not in the U.S.
Hope your Mom continues to do well with her recovery from the surgery.