Tim,
I understand your concern. I also had head and neck cancer (squamous cell carcinoma), and the resulting radiation closed my throat completely. I also had my sense of smell and taste altered radically, and after some other problems ended up on a feeding tube. I lost 35#, more than I had to lose.
The one thing I could tolerate most of the time was ginger ale. You are right that anything with calories is good, although she does need a good supply of water too. I could not even stand the taste of our wonderful spring water. See if you can get her to drink milk, or flavored milk, which has calories and protein.
My advice is to buy one of everything you can think of to try. Commercial yogurt drinks are less dense than smoothies and easier to drink. Ice cream goes down easily and has a good mouth feel; see if there is a flavor she can tolerate.
Colder is often better. Try popsicles and anything frozen. And jell-o? From what I've read, loss of taste due to chemo doesn't last as long as from radiation (that can be permanent; mine comes and goes after 17 months), so maybe this will go with time. I've also read that sweet, and sometimes sour, tastes are usually more tolerable than bitter ones, so that might help.
Now that most things either taste right, or don't taste at all, I've been able to regain about 12#. I hope your wife has similar good fortune soon.
Susan