i need an answer?

my daughter who is 17 has been asked to do stock take in a shop she works in part-time. her normal hours are thursday 4 hours and sunday 6 hours, it is in her contract. she is studying for her A levels and I really dont want her to do it as it will interfere with her study, the stocktake is this evening starting at 6pm until whenever it is finished, probably after midnight. i am doing a night shift and wont be able to pick her up but her manager is saying she HAS to do it. Is that really right?