That's great that she's eating the Wellness a bit better now.
You're right, sometimes they seem a little confused about how to eat the canned food. If you're using a bowl, I would suggest a saucer or small plate instead. They don't like the idea of getting the food on their whiskers, I think. My favorite is a saucer w/ just a little raised bowl shaped edge...it's the best of both worlds as some of them will just push the food off the edge of a completely flat plate.
Some of mine eat better when I move the food into a little pile after they've scooted it around on the plate.
How much food per meal or per day depends on her weight, the food, and metabolism, etc. My cats average about 3/4oz-1oz per lb of body weight, per day. My fairly inactive 13lb cat eats 9oz a day when he approves of my food choices, he'll get by with 6oz if he gets picky.
My 10 month olds eat about 1oz per lb, per day. Some of the Wellness flavors are pretty high calorie (which is fine) but they will normally eat less of that then something "lighter".
I hadn't heard that about UTI's with Wellness. Doesn't mean it's not true, but it's interesting. In a cat with existing urinary issues, it's best to avoid the fishy flavors of any food. I woudn't go heavy on the fishy ones with any cat, but in moderation it's fine. That's the only possible connection I can think of, but that could happen with any food.
With that in mind, we have only tried the beef/chicken, chicken, and turkey Wellness...because of Beandip's bladder issues. He's picked raw over canned, so I will probably let the others try some of the fishier ones soon.
Especially if she's a little chunky, you don't really want to restrict her too much throughout the transition, as a drastic caloric restriction is more dangerous for a chubby/fat cat. How 'chunky' is she? Are you trying to go to a completely canned diet? I think with some cats it's harder to get them to eat the canned if they know they'll get the dry at some point. What I mean is that "50/50" dry/wet is hard to acheive in some stubborn ones. With some of mine, it seemed to be all or nothing. My schedule allows for 3 meals a day, so for the stubborn ones I had 3 chances to get "enough" food in them throughout the day, when we were transitioning. Now they do much better. I have a couple that I still have to keep an eye on, but they are maintaining their weights and getting better and better w/the wet food. I think I didn't really answer your question...it's all kind of confusing. Let me know if I can clarify.
The foods that Sharky mentioned are good for getting them used to eating something other than dry food. Oddly enough, my most stubborn dry food junkie, Precious ...finally got on board with Natural Balance canned food. Funny because it seems like health food to me, but she loves it and she started doing much better after I offered her that. Now she'll eat almost anything I offer. Every cat can be different, though.