Yes, the sore throat will be from the anethesia during the operation(s), etc. That's normal for operations I think.

Like jacq knows from experience, I wouldn't think the wiring itself will hurt; mostly just the original operations/doing of it (kind of like when they first put your braces on only 10 times worse but after a bit it doesn't hurt anymore).

I found this hospital page with a "wired jaw diet" complete with recipes. Maybe it can help with what to fix that will be a bit of a treat/fun and good for her and another from a nutritionist :-) I may be way off-base but I think the "thickness" issue is just in the beginning when she's healing from the operation effects themselves but later, when her throat is feeling better, etc. she should be able to handle anything through a straw? The supplemental drinks are just as "viscous" I think as anything else would be that wasn't pure liquid.

http://library.umsmed.edu/pe-db/pe-wired-jaw.html

http://drirene.healthandage.com/qa3/qa130082.htm