Hi, Colleen--
Cats can be so fussy! If you want to take it really slowly, you can start by just placing some of the wet food next to her dry food (on a plate, or in another bowl, if you don't think she'll eat all the dry food immediately--it's bad to get dry food wet and let it sit for more than half an hour or so). Or you can try mixing it. Most people (including me) think it's ok to leave wet food out all day for the kitty to nibble on, until 2 hours before test/shot time.
Some cats who don't like other wet foods do like Fancy Feast and Friskies--I think the flavors are pretty strong. But if she turns up her nose, there are a few other strategies you can try. One is warming up the wet food a little. Another is sprinkling it with parmesan cheese, which some cats love.
If you can't get her eating canned food, you could try switching to a lower-carbohydrate dry food for now--that's probably not the best thing in the long run, but because she has lost a lot of weight very quickly, I think it's very important that she keep eating and not lose more right now! Here's a lower-carb dry food that is relatively easy to find:
http://www.evopet.com/products/1441 . It's kind of expensive, but she would not need to eat as much of it; it's pretty high in calories. Most cats seem to really like it.
Fortune, help your mom out here--let her test you, and eat the good food she offers you! She loves you and wants what is best for you!