If the fish is an adult, and the colors in these photos are accurate, then your new fish sure looks like a female. My paradise fish ate the same as all my others ~ a combination of freeze-dried tubifex, two kinds of flakes, and live or frozen bloodworms (I'm a big believer in a varied diet tailored to the species). If your paradise doesn't want to eat, feed your guppies their normal flakes, and ~ if she's a healthy fish ~ she'll watch them & pretty soon join in. In my experience (decades) many fish don't care for hard food in a pelletized form, which it sounds like you're using. Also, are you sure your tank isn't too warm for her? Paradise fish do not like a tank that's too warm.
It goes without saying that if anything in any tank is off, we all test our water parameters for ammonia, nitrite & nitrate, right?
Good luck. Linda.