If your sister has a low appetite & small diet but is sufficient it’s fine, you can’t compare someone who has a diagnosed eating disorder to a different person.
presumably your parents are more focused on ensuring you establish healthy lifestyle & diet, and are going to be more focused on you in the circumstances & establishing healthy behaviour and can trust in the future when they are not monitoring you, you will keep this up.
if a non-alcoholic has a few drinks too many and makes themselves sick, everyone knows thats a poor behaviour but in isolation is not really an issue. If an alcoholic has 1 pint everyone notices as they know the damage that 1 drink can lead to.
Focus on yourself.