Is there anything that can cure this?

Jealousy is not only a lack of confidence, but a lack of love for yourself. You need to be happy with what you've got....nevermind your sister. The more you focus on her, the more negative thoughts you will create in your head. Instead of being jealous, be happy that good looks run in your family. I'm sure you are just as pretty, and there probably others who are jealous of you. Be happy that you are attractive...and think of all those people out there who are not as fortunate.