School has picked our 14 year old to mentor the new grade 6 kids. She's flattered and worried

Email came yesterday. She's one of six students asked to be a 'buddy' for the new grade 6 batch this year. Lunch with them once a week, show them around, be someone they can find. She was thrilled for about an hour. Then she worked out it's her lunch break, the one time she sees her own friends. She wants to say yes and is scared it eats her whole year. We've told her she can try it and step back if it's too much. Is that how it works in practice, or do schools expect you to stay once you've signed up? I genuinely have no idea.