My sister wants to start losing weight and might start counting calories, I don’t want her to do it somehow? That makes me want to eat less??? I feel weird like idk like jealous im so confused

I’m a 14f teenage girl and my sis is 17 rn. basically ever since grew up I was slightly bigger but like just today, she was saying oh she wanna start losing a bit weight for the summer bod. Idk it started to affect me( I have an eating disorder and lost 30lbs) like she wants to start counting calories and stuff. It’s not fair cuz she can pay for those apps where the picture can scan how many calories are there. Idk why am I jealous?? I like don’t want her to do it and stuff I don’t know what is this feeling?