Thank you all for the wealth of knowledge. I've been feeding my cat a third of a 5.5 oz. can 2 times a day, with a few treats here and there. She hasn't lost any weight, and she's extremely active and seems happy. I had no idea about the caloric content of the WeRuVa canned food though, so I am really happy I asked my question. I have tried mixing food, but she simply won't touch it when it contains the pate-style food, which most canned food seem to be. She'd rather starve, I suppose. I really wish she would eat the Wellness canned food, because I have about 20 cans of those.
Fortunately, I can donate it to my local shelter (where I got her from).
The only thing I know she'll eat for sure is the Fancy Feast grilled turkey and chicken.