In our case they do blood work before every dose. So far all the blood work has been great. We are doing a scan next Friday just before round 6 of chemo. I know that everyone's protocol is a little different so I would ask.
As for the nausea we haven't had a lot of that but I can give you some hints that might help. First off - what meds is your sister on? We have Zofran (ondansetron) and Compazine (Prochlorperazine) along with Dexamethasone.
He takes the Zofran and Dex twice a day for two days after chemo then the Compazine every 6 hours. He can take the Zofran up to once more if needed. If she's not already doing something like this then I would talk to the ONC about getting going on something similar. If she's already doing this then it going to be figuring out when she CAN eat and getting as many calories in as you can.
Try waiting 30-60 minutes after taking anti-nausea medications before trying to eat. This gives them a chance to work. Also take them as needed at the very first sign of nausea before she throws up.
Foods that are high carbohydrate such as pastas, bread and potatoes are easily digestible so that empty out of the stomach faster. Red meats often have a heavy metallic taste for people with chemo....if she has that I would avoid them. Chicken seems to go down better. Stay away from heavy spices as bland works better. It sometimes is a matter of trial and error. The biggest hint I can give you though is NOT to eat a favorite food if there is any nausea - it won't be a favorite food if you throw it up.
Something like protein shakes in small sips may help too. We used frozen fruit, a couple of scoops of ice cream, vanilla yogurt, protein powder and then enough milk or Ensure to make it a milkshake. You can make them any size and keep smaller sizes in the freezer. GNC (our local health food store) has a bunch of different flavors of protein powder. We used unflavored that I hid in almost anything from yogurt to cottage cheese even mashed potatoes and soups then we used Cookies and Cream for the shakes.
Hope this helps!