I’ve already said this to you and i’ll say it again – do not let her, or anybody else for that matter, treat you like an option. She’s already done it multiple times and every time she does she knows you’ll let her right in. You need to stop her from doing that. If she comes back again, you need to get your emotions in check and flat out demand that she either commits to you or takes a hike. And if there is even a tiny bit of indecisiveness in her response I would strongly recommend moving on and never looking back. Take care of yourself first, man. You deserve someone who commits to you and loves you as much as you love them. You can’t let someone tear you down like that emotionally no matter who it is – your best friend or your significant other.