Questions I have been asked in many interviews, not just NICU interviews, were:
1) Why nursing?
2) How do you handle conflict?
3) Name a time when a coworker was doing something wrong, and what you did. (Actually, a lot of 'name a time when...')
4) Why do you want this area of nursing?
6) Why should we hire you over someone else?
7) Where do you see yourself in 5 years?
They are pretty basic interview questions. The ones that stump me the most are always the "name a time when" questions bc you never know what they're gonna ask. The others are pretty easy to come up with answers for and be prepared with. Just search the forum or Google interview questions for nursing jobs. Unless your mother has any experience in a NICU previously, I doubt they will have a ton of NICU-specific questions for her. Good luck to her!