Could be the warmer weather, I noticed mine decided to start being picky. Turned out they were bored, just as we had bought 24 x 800g cans of their normal wet food
So anyway I got a few different ones to try, do be careful though mine seem to have cast iron guts on the whole so doesn't affect them changing.
Applaws is a good food for being popular, but it isn't a complete however aslong as they are eating the biscuits then that's ok.
Even if you try similar foods to whiskers like Felix or Sheba and gauge if she eats it, if she does then least you know there is no actual issue, and she could just be being picky