“Mean Girl” at work

I (36f) work on an all women team (45-58f) that I typically enjoy. We had an open position that we filled about a year ago with a candidate that I really liked. She was charismatic, answered questions really well, and passed out handouts of her slides when the office randomly lost internet. I was impressed!

After hiring her, I learned that we’re in the same doctoral program (she’s a year ahead of me) and I loved asking her about what’s to come. After 2 months of her being there, my direct supervisor (let’s call her Patty 48f) told me not to trust her. I pressed and she told me that the new hire (Sarah 54f) had told her and my director (Maria 50f) that I “wasn’t smart enough to be in a doctoral program”. Why she felt comfortable telling Patty and Maria that, I don’t know. How it came up? I also don’t know. I also don’t know what the reaction was in that moment. It got worse with Patty telling me things that Maria, Sarah and another woman, Laura (56f) were saying about me. I asked Patty to stop telling me and it continued. I told her that I feel as if I’m being bullied despite none of these things being said to my face. I stopped coming out of my office for about 3 weeks unless it was to go to the bathroom or go home. I am the youngest on the floor and felt really lonely during that time.

Our office had another department added to our floor and I made friends with some of the younger women there (mid 20s to early 30s). They also suffered bullying at the hands of Sarah, Maria, and Laura but it was always 3rd hand information or passive aggressive remarks. It got to a point where during a team event where people came in to ask about what the office is doing well, could do better etc most of the people in our building (about 30 of us) put down that Laura had been bullying them. HR was called a few months later and Laura has been kind ever since.

Fast forward and we have an open position who would report directly to me. One of my cohort members applied and she (Amelia 25f) was moved forward for an interview. Before her interview, Patty let me know that Sarah sat her and Maria down to “express some concerns” about Amelia. The first concern was disclosing that she has an “illness that causes her to not show up to commitments”, a “3 year old son without a father to help”, and a full-time job elsewhere that “she’s not planning to quit”. All of this was said before Amelia interviewed. Amelia knocked it out of the park and was offered the position. She thanked me for my help and let me know that Sarah had sent her a text a few days before the interview saying “I’ll put in a good word for you 😉” and then text her again saying she spoke with Patty and Maria about her.

Today I let Sarah know that we chose Amelia and I was happy to have her on board. Sarah went to Maria and then Patty to voice “more concerns”. I was called into this meeting and had to do everything in my power not to lose it. I know she’s going this hard against Amelia because she’s threatened by her, but I’ve never seen anyone act like this in a professional setting.

I’ve worked with Amelia before and I feel she’s great! We get along really well and I appreciate her insight. My team was really thrilled with her too during her interview.

After thinking about it, I decided to report Sarah to HR because of her disclosing Amelia’s illness and her being a single parent as a deterrent to her being hired. It hasn’t been made public to my department yet but it eventually will.

My question (besides wtf) is how have you navigated political situations like this? Have you dealt with someone like this before? And how do I protect/support my new coworker?

I can provide more info in the comments as I feel this is pretty long. Also, on mobile, so formatting.

TLDR; I’ve had issues with some women in my office. One in particular disclosed medical info about a candidate to prevent them from being hired. Hired anyway and still campaigning against the candidate.