It is the same project, yes. She was having work-related depression, as in having trouble finding the motivation to work and had a lot of free time on her hands, so I thought I’d invite her since it was a field she was interested in and could learn new skills. She indeed found it interesting and involved herself deeply, we did many things together and had plenty of fun.
There was no “supervisor” to speak of, although everything is in my hands and I was showing her around, explaining things and so on. She had the full freedom to be creative, at her own pace.
My “friend” was on a “break” from it (as in, not really caring), then he came back, noticed her and was furious about his “authority being challenged”, also started to belittle her work and challenge her, and she challenged him back.

“And also, when your “friend” started slandering you recently, did she believe him? Are you in danger of getting fired from the project?”

I don’t know what she believes or not since she’s been refusing to communicate and cut me off. Considering how her treatment of me shifted towards vile, I assume that he did fill her head with a lot of nonsense. What makes zero sense to me is that she seemingly forgot just how much she criticized his poor personality, social skills, work ethics, the way he treated others and the abuse he subjected her to. The very moment he stopped being nasty to her, she betrayed me and was on his side, despite not really knowing anything about him as their previous interactions have been very scarce and mostly involved fighting. Our mutual friends are also very critical of him as they have experienced first-hand his poor behavior and personality, and have advised her to not involve herself with him, which fell into deaf ears.
As for being fired, it is my project and fully in my hands.