vent away tracr!
I will assume you recognize the see saw up and down pattern you are on. Its not healthy, nor productive (you know this). By responding to her tactics, you are reinforcing them as valid and training her that they work. Also there is likely a certain comfort to her that she can control you and get the response she wants with her behavior.
Just some observations to think about, dont let that stop you from venting!
I know, you're exactly right. All I've accomplished is reinforcing that she can bully and threaten her way into getting what she wants out of me. I think the only reason I gave in this time is that it was the first time I really felt like she would have followed through on the threats. I see now that I was wrong about that too. I guess knowing that I had actually made a mistake and caused all this crossed my mind too. It's just so tiring having to always be so careful and analyze everything you say and do before you do it to try and minimize the impact on them. Thanks for listening.