Hard to drink/eat due to nausea?

My mom already had her third chemo for cancer, but due to a bowel obstruction by the tumors, she has a PEG tube in her stomach to gravity drain the bile. Anyways she had prior to that an NG tube down her nose/throat for weeks and it dried her up. She is scared/having a hard time with eating or drinking (often makes her gag/throw up)...any ideas on how to ease back into eating and or/drinking so we can get her off the TPN intravenous feeding?