I honestly would not worry about the cats getting fat from eating canned food,I believe that's a myth and in a case like yours I definitely would feed her canned.
My 3 cats each get a tablespoon of canned twice a day and they are certainly not fat,they free-feed on good quality dry.
It's also easier to mix any kind of meds they might need.
I would also think a dish for each cat would be better,otherwise you don't know who is eating,or how much.
When it comes to nutrition,the vet does not always know much..
"The cruelest animal is the Human animal"
3 kitties,Rocky(r.i.p my boy),Chico,Vinnie