Sexual partner saying my primary partner is mistreating me.

Hello I think this is the right flair to use, looking for advice!

For context I (22enby) am in a non monogamous relationship and me and my partner (22enby) have been together for over a year. Something upsetting happened today. One of my sexual partners (21 f) (friends with benefits situation) wanted to talk to me, where she sat me down and basically expressed concerns about my relationship with my partner, and that my partner was seemingly mistreating me. This came as a shock to me for many reasons.

1. Md and my sexual partner just started being close about 2 months ago, and have only hooked up a couple times, and I haven’t talked about my primary partner too much with her.
2. She has no evidence to support this claim that my partner is mistreating me, other than vaguely referencing my primary partners behavior vaguely and without any specific examples
3. She brought up concerns that are irrelevant to my parter such as addiction and suicidal tendencies, which they do not suffer from (unless u count nicotine)
4. She has only interacted with my partner face to face one time.
5. I have been abused by my mother my whole life and I know what abuse looks like, it’s something I am very educated about, and I’ve been in therapy for it for over two years. I’ve made a lot of progress in my own recovery and I would know if I was being mistreated. I talk to my therapist about my partner often, and he has never expressed ANY concerns within the realm of my relationship with my partner being abusive/ toxic. And neither have any of my friends that I talk to about my partner.

My sexual partner also brought up her own experiences of being in an abusive relationship with her last girlfriend during this conversation, which I knew about and was pretty terrible. To me it seemed like she was hardcore projecting onto this situation because of her trauma.

I talked to my partner about this and they were very upset and hurt by it, as was I. My partner and I have had our fair share of issues but our relationship is very stable and makes me very happy and fulfilled.

I just don’t know what to do about this situation, I feel like my sexual partner was not listening to me or my experience of my relationship with my primary partner at all. I felt like she was trying to almost gaslight me into thinking I was being abused by my partner. At the same time I have empathy for her experience in an abusive relationship. I feel angry and confused, and I don’t know what to do going forward. I’m not afraid to cut things with my sexual partner but I’d rather resolve this, but idk how to bring it up again.