You are WHO you are and you DO have a talent, maybe it is not as good as your sisters, maybe it it is actually better than your sisters. You are unique in your own right, there is no one else like you. Be happy with WHO you are and what you can do. Like the Army ads say "Be all you can be" and forget the small stuff.

She may be one that need a lot of encouragement to keep on and do better while you have always excelled on your own... I can promise you, your parents do not love her more than you, as a parent who raised 4, I know we love each child equally, it is just that some require more attention than others. My oldest son could entertain himself, didn't need watching or "mothering". My middle son required a LOT of attention, constant encouragement and demanded a lot of my time. My daughter required little of my attention and she had to be handled with a very gentle touch as her feelings were easily hurt. My youngest was the most demanding child I ever saw. He was not a bad kid, just wanted all the attention and was quick to cry to get it. He also use to do the cutiest thing to get attention.

So think about that... Is she one that NEEDS constant encouragement and you are more independant and do better when left alone? Go away from this with this; Love your sister for WHO she is and love yourself for WHO you are.