Two Potter's Two Prophecy's

What if Harry Potter had a twin?
What if his twin was in a prophecy?
What if she possessed ancient forgotten powers?

Rose Potter is not famous like her brother, in fact she's a completely normal witch. She grew up with the Weasleys because she didn't need protection and she adores flying she's the best chaser out of all the Weasleys, so why can she do strange things and why does she glow without her enchanted bracelet?