That is a beautiful cat, such striking classic tabby markings; and it sounds like she has a great personality as well.
If the friskies she eats is dry, try switching to a higher quality dry. Like you said 1/2 friskies half the better food, then *slowly* increase the percentage of the good quality food day-by-day over several days, until it's down to just a few pieces of the friskies on top. By then hopefully, she will equate the smell of the mixture as something she is fond of and go for it.
If she eats wet friskies, if I remember correctly, there are some of the pate formulations that are high protein percentage and low carb. Not the best quality food by any stretch, but not horrible either, and better than dry-only.
Jeff & Nala
Simon and Penny, waiting patiently at the Bridge