I do think that she is crossing your boundaries. I don't exactly have a sister like that, but we have issues, and one thing I know for sure is: if you don't talk to her about it nothing will change. I never talk to mine about our issues, and it just gets worse.

Maybe, when it seems like the right time/ when she's calm and in an okay mood, you could try to talk to her about it? She might not even know that you find it an issue. Since you'd been helping her out all this time she may be attached to you and doesn't know how to express that very well.

I hope things between you two get better soon