A constant diet of high protein food (like your turtle is on) will eventually cause shell problems (pyramiding). It will also tax internal organs and is likely to ultimately shorten your turtle's life.
Your turtle prefers those foods to pellets because that's what she's become used to---she's become fixated on them to the exclusion of other more balanced foods. And you keep giving them to her, so she'll keep eating them.
Given the choice, the majority of turtles will opt for high protein foods over, say, veggies. (In the wild, these foods are more nutrient dense and since wild turtles might not be eating every day, such foods help sustain them.) For captive turtles who don't have to worry about their next meal, however, this is not healthy, as was explained previously, and it's up to the keeper to provide balance in the diet.
I looked at the link on Taiyo, but it didn't say how much protein, etc. the food contains. If you look at the container, there should be something written on the side.
BTW, bloodworms aren't all that healthy are should be given more as a treat.
Hard to say about the hind legs. If the legs were banging against the tail, it could be because of constipation. Kicking her hind legs backwards means she's digging???
"You become responsible, forever, for what you have tamed." -Antoine de Saint Exupery-