How do you know if my sister is jealous of you?

Do you mean if your sister is jealous of YOU? If so:

Well, she'll start having a bad attitude towards you, as if you did something mean or something to her, and she'll probably say that you're constantly bragging (even if you aren't). She'll start complaining about how you are constantly taken for better than her (or she may say you are better than her). She might start copying you, and constantly bring up the subject. She may even brag about being able to do it as well or near as well as you can.

On the other hand, if she's the other type of sister, those wouldn't be as harsh (the things listed above) and she'd still love you and all. If she were even better than that, she wouldn't show or feel jealousy at all. But I've seen many siblings who aren't like that, and it's not uncommon.

~OneAndOnly13

you can always tell becuase she will start acting like you and want the same things like . and she will also ask to barrow things of yours too. and wants to hang out with you and your friends .

i also have a nine year old sister that wants the same snooki boots .