Buttercup, Hi-
One of the items I always had in the pantry was Pedialyte
[flavored or non-flavored] found in the "Children's" section of the gro store. This was not for calories, but we used it as a SAFETY measure against dehydration because it has lots of electrolytes. Liquid jello[ cooled to the degree she can tolerate] might also be soothing.
And for what's it's worth, I am a firm beliver in pegs. Hope she does well. Amy