if she isnt looking too skinny then i would just fast her until she eats them, you can soak them in some tank water with the krill or something before hand to make them smell like what she wants, and use slow sinking/sinking types so she doesnt have to come to the top if that is an issue for her, fish can be pretty darn stubborn sometimes when it comes to switching pellets but you just have to be even more stubborn and in the end her stomach will win out, a healthy fish will never starve to death if there is food available