PIP'd coworker conflict, needing advice

Edit: [Here's a link to the 'raw' version of my writing before I asked AI to tighten it up and layered in more context.](https://www.reddit.com/user/courageousmushroom/comments/1sjk3pq/raw_version_pip

Edit: Here's a link to the 'raw' version of my writing before I asked AI to tighten it up and layered in more context. I’m the only junior (3 YOE) on a 15-person specialized team at a big MSP. Everyone else is a solid senior except one mid-level coworker. I’ll call her Stacy (11 YOE, with us just over a year). Stacy was a senior at her last job but didn’t meet our team’s standard for senior. She constantly reminds everyone about her years of experience and how she’s done X/Y/Z for 8-10 years. We’ve been paired on a lot of projects with independent tasks. Early on she avoided technical work in many creative ways and leaned on me heavily for step-by-step help, always with excuses like “I’m just getting back into it” or “I have more experience with other tools.” I helped because I figured she was trying to learn, but she was just extracting the solution and not internalizing it. Then she slipped and bragged to me that her previous role was "leading a dev team as their ticket coordinator". That's a different story than what she has been telling everyone, and that made a lot of things she was doing start to make sense. I realized I was enabling her, so I started giving higher-level guidance instead of hand-holding. Her attitude flipped and she frequently accused me of being “cold”. She started going to seniors for help, but they didn't keep it private and openly corrected her when she claimed to do things that they helped her do. Next project she pushed hard to be the “lead.” Manager assigned me as lead and her as support. She got salty and started doing petty stuff in front of clients, the team, and our manager to try to make me look bad (it never works, and often exposes her misunderstanding and bad judgement). I documented everything for a while to spot the patterns and had a quick chat with my manager for some guidance on what to do differently to influence different behavior. He told me not to change anything and that I wasn’t the first person to raise these issues. EOY review time: Stacy self-rated top rating and expected a senior promo. She called me crying after her review - she got the lowest possible rating. Management explicitly compared her to me (specific examples of where I outperform her technically and professionally) and told her she wasn’t even meeting mid-level role expectations. As an adage, she frequently calls me just to vent about her personal issues and I don't understand why because I do not provide emotional soothing or engage with it at all. New project: Stacy was given explicit ownership of a non-trivial technical task with a hard go-live date. She’d been telling everyone she was an expert with the tool. Two weeks before go-live she said things were tested and ready. I (politely) asked to see the test outputs, she yelled at me for questioning her. That got manager attention, she wrote an essay describing the outputs instead of showing anything and got pulled from the project and then from all client-facing work - except the project where I am lead (yay). She's manipulated the client into contacting her first for everything, advised the client to assign all tasks to her for her initial review, excluding me from meetings and emails, keeps discussing things that she genuinely doesn't understand. She's been corrected by our manager about all of it twice and gets emotional and ignores my direction to our agreed operating model. This and everything else is just tip of the iceberg. I recently saw (by accident) that she’s now on a PIP. I’ve started declining her calls and asking her to put requests in writing. She keeps saying she has suspected ADHD and that I need to accommodate her “preferred communication style” and answer her calls and I feel like she's creating a trap. I’m exhausted. My manager said I'm getting promoted to midlevel this cycle. I've been working hard for it and all I can think about is how she will predictably react badly and escalate the weird passive aggressive stuff even more. What's the play here? Just keep trying to keep it clean and hope for the best? I'm not worried about myself professionally, I just don't know how to work with this situation in general. PIP is really uncommon at my org so I don't know what to expect or predict. Genuinely, any practical guidance would be really helpful. I've been keeping this all to myself because I know this is all dumb as hell.