That said if that's harder to do when she's this old now, then ask her why she's eating the sugary foods. Is it because she's hungry, is she thirsty and mistaking it for hunger.... Or is it because she can ?
If she takes them from your room, that's going into someone else's space without permission. But even if she hadn't and you were dividing up sweets amongst people, you could use that to teach a bit about supply and demand? That the candy /sugary things are a finite resource and that there is only so much of it, so that is why it should be consumed sparingly?
Not sure
When was the last time she ate herself sick? Not that I'm recommending it, but when she eats junk, does she eat enough to feel bad? Does she notice how her body feels when she eats "good" vs "bad" foods? What kind of information is she getting about health and her body? You need to be talking about these things, a lot. As she gets older, she is going to be more responsible for what she eats, so limiting quantity isn't as good of a strategy as when she was little. She needs to find her own reasons not to exclusively eat gummy worms and pizza, and to do that she needs information about how food affects her health, and to know that you care about her and how she treats herself. If she knows you care, she will treat herself better. Maybe not immediately, but the message will get through. Let her know why you limit sugar snacks for her, her sister, and for yourself. (It's because you love her ❤️)
Teach moderation Even at 11 you can still possibly teach that Demonstrate it in what you do. If you go for more while fruits more often than candy, then that shows her that whole fruits are a better sweet thing.