Sounds like a bit of sibling rivalry. You two are teenagers, or so it seems? You just annoy and bug each other. You might not have control over her behaviour, but you can control how you react towards her behaviour. Locking yourself in your bedroom and not going to the bathroom doesn't solve anything. I'm not agreeing with her behaviour, it sounds pretty childish and petty to say the least. But for goodness sake, don't buy into her pettiness ... "chasing" her and "screaming" at her solves nothing.