Getting cat to gain weight

Coco returned home from her I-131 treatment last Friday.  She had to be off the tapazole for 2 weeks prior to treatment, and got down to a super skinny 7.8 lbs.  She was 14 lbs last December, and has the build to be 12-14 and still be in a healthy weight.  Our goal now is to get some weight back on her.  She's stressed out being confined to one room of the house, so Auburn and our local vet have suggested feed her anything she will eat for now, just to keep her eating.  Currently, that is Friskies canned food.  Saturday it was Meow Mix.  

I would like to mix something a bit healthier in there, but don't want to risk her not gaining weight.  I know the "junk" food should help with that.  Any suggestions for food?  She normally eats Science Diet Optimal Care dry food and Wellness canned, but won't touch either of them right now.  A coworker strongly recommends Blue Buffalo, but I know nothing about it.  

I recommend Nature's Variety. It's a very high quality protein, good quality food. It'll help put muscle back on and give her the protein she's been lacking in the Friskies diet. Also I'd think about giving a good probiotic like Prozyme. This will help replace that good bacteria that's lacking and help her digest her food. Blue Buffalo is also a good brand, I just prefer NV myself. 

My cat had that about a year ago. It was before I discovered TCS, so I didn't know as much about nutrition, but one thing that worked for her was plain meat baby food. Make sure it doesn't have opinions or garlic and I rotated thru chicken, turkey, and beef. Once she was at least eating that, I mixed it with her canned food, it was Royal Canin Recovery r/s. she ended up with CRF and I spent a lot of time trying anything she would eat. Another thing that worked short term was the water from a can of tuna. I found once she got something in her belly, she was more likely to continue eating, of she stopped, it was really hard to get her to start again.

Did the vet give you any meds for her? We got an appetite enhancer, something to help w her upset belly, probiotics, an omega3 supplement, an antibiotic and one other med I can remember. They might not have all been related to the iodine though, we were hoping the kidney issues were related to her thyroid but unfortunately they weren't, so some meds were to combat kidney stuff before the official CRF diagnosis.

She wasn't sent home on any medicine, but is now on Flagyl and prednisone due to her stress causing IBD.  They feel it is temporary and will resolve once she can move freely.  

Her blood work is actually the best it has been in years!  As of now, they don't suspect any CRF showing up as the hyperthyroidism resolves.