Help with chemo sickness

My mum is on her third week of chemo- she has it for 5 days once a month. She had it for 6 weeks before alongside radio but never had any sickness, just a bit of nausea but this was controlled with anti sickness. She took her chemo this morning (day 1) and has had 2 lots of antisickness but she is really sick today and I just don't know how to help. Is this normal? Why is she suddenly being sick and the antisickness isn't helping at all? I wish there was something i could do to make it all go away.