Hey there... unfortunately this is very normal. At this point she may need some pain meds. It's best if she takes the water or fluids lukewarm that way it doesn't startle her already sensitive mouth. Definitely the baking soda rinses will help not with pain but with healing (she can also flatten club soda and actually drink it... it has healing properties - much like the baking soda mixture) I would eat and drink what I could then rinse and sleep - a pain med prior to eating (usually 15 minutes - 30 before hand) then maybe magic mouthwash and chug or eat what she can.

best of luck... it is not fun. I am assuming she is at week three almost?

Cheryl : Irritation - 2004 BX: 6/2008 : Inflam. BX: 12/10, DX: 12/10 : SCC - LS tongue well dif. T2N1M0. 2/11 hemigloss + recon. : PND - 40 nodes - 39 clear. 3/11 - 5/11 IMRT 33 + cis x2, PEG 3/28/11 - 5/19/11 3 head, 2 chest scans - clear(fingers crossed) HPV-, No smoke, drink, or drugs, Vegan