Hi and Welcome to the Forum
I'm not suprised your turtle hasn't eaten the fish - she's probably too full to even chase a fish. How much they should get depends on the size of the turtle and what stage of life he/she is in, but I can almost guarantee two palm fulls a day is way too much.
Here's the basic rule of thumb: Up to 4" length, every day a turtle gets as many pellets as would fit in his/her head if his/her head (not neck - just head) were hollow. After 4" length, cut the amount back to a headfull every other day.
If you (and your turtle) prefer, you can break the daily amount of pellets up into several small feedings just so you don't go over the total for the day. For instance, I feed my 7" male a half a headfull of pellets every day since he enjoys feeding time sooooo much.
For the rest, they can have green leafy things daily - as much as they want so long as they don't get the runs - in addition to the pellets. In addition to that, they can have a couple of servings a week of other veggies and some fruit like blueberries, carrot, tomato, bell pepper, steamed sweet potato, etc. In addition, one a month they can have a high protein treat like a few freeze dried, gut-loaded crickets, some shrimp, boiled chicken or live minnows. On the days they get the high protein treat you can skip the pellets.
Here's the complete version of turtle nuitrition. Be sure to read every word. Then read all the other stuff on the site - it's very helpful.
http://www.redearslider.com/index_nutrition.html