Hi haven't read other replies but administer chemo as one of the aspects of my job.
Sometimes people will be OK with their first course and then it "hits" them with the second course.
What anti sickness meds is she on currently?
If she is currently on intensive chemo hopefully she will be having a drug called Zofran (also known as Ondansetron) twice a day.If she has a "Central" or intravenous line this should be being administered intravenously by staff prior to her chemo.
If this alone is not working the staff may be trying a drug called metoclopramide in between times.
If this doesn't work sometimes a small dose of the steroid dexamethasone can be effective for nausea,this is often at the discretion of the registrar/consultant as your Dsis may already be on steroids as part of her chemotherapy regimen.
Sometimes if the nausea is very bad people have been known to be put on a "Syringe driver" which is a device that infuses a small dose of antisickness consistently over a 24 hr period.
Other "adjuncts" (Additional drugs) sometimes tried are the anti sickness drug "cyclizine".Sometimes low doses of drugs such as "Lorazepam" are used if other things fail but again at consultant/reg discretion because of the sedating effects.
Some units may employ a psychologist who can advise on visualisation/distraction techniques fpor patients,especially if their nausea is "Anticipatory" ie the smell of the food,knowledge their chemo is iminent is triggering the nausea.
If she is unable to eat much then on our unit we often freeze the nutritional drinks(Fortisips and the like) that come in cartons,then the patients can suck them like ice-lollies,good for if mouth is sore too.
Sorry for long post!Hope it helps a bit.Good luck to your Dsis xx