You have too much passion to consider suicide. If you die what will happen to your stories. Honey stay strong and treat those girls like the ants that they are!
Well if you have the dates when the story was made then that's proof that it was your story. If you have rough drafts to that would be a good way to show it's your story. But honestly if you want to get under her skin when she glares at you and points at you don't get mad, instead, smile and wave and while mid waving turning that hand into the glorious "f*** you" sign just quick enough for her to see. Turn the tables on her. If she calls you a b**** just laugh and say thank you. Say your insults with a smile. It will feel amazing trust me. If she accusing you of something don't yell at her in denial that would make you look bad especially if she cries. Instead, say "who me? I wouldn't do that!" act surprised. It would help even better if you have some friends to back you up and just laugh anytime you pass her. The change in direction of your attitude will definitely throw them a curb ball.
Hmm it would also be wise not to reveal anything of your plots or stories. And they are not your real friends if they've done that to you.
It sounds like she's just being an attention-getter. But by all means, control yourself around her. A calm, smooth person who's in charge of their feelings is way more dangerous, respected, and allows you to avoid any event that can cause really bad consequences. Talk to her calmly. Say something like
"(her name), it really upsets me how you're unable to come up with your own original work and have to copy off of other people like me. Perhaps you need a lesson on creativity? I can totally give you that, if you want. But otherwise, if you keep stealing my stuff, I'll get you in trouble for it."
Again, say this calmly. It'll likely embarrass her and make her stop. If she interrupts you, make an exaggerated gesture, such as rolling your eyes or sighing, and say "Wow, you're not even mature enough and able to listen to me, let alone come up with your own stories."
DO NOT ADD ANOTHER WORD. NO MATTER WHAT ANYBODY SAYS OR DOES. JUST STAY AND/OR ACT CALM.
This'll score you points.
And the fact that you're suicidal, I hope you feel better soon. Alright?
And if writing's your passion, (it's mine as well) then don't stop. Don't ever stop. Write. Create. Form. Imagine.
Don't worry. You can hire me to beat the living hell outta her and sell her soul to Satan.
Wow, now that's a vent.
Hope you feel better unloading all that.