How to tell my mom (54F) that I (21F) was SA’d

I don't want to type out the entire incident, but my best friend (21M) of six years raped me a few weeks ago. It was a complete shock to me, I was saying "No" and "Stop" over and over, and physically trying to get him off of me for a solid half hour before I gave up. I was bleeding afterwards, and he left bruises on my legs and chest, which I did take pictures of, if I choose to report him in the future, but also as a harsh reminder to myself that he is not the person I thought he was. I've been feeling different and kind of "empty" since it happened, having difficulty focusing on simple tasks, not feeling present, sleeping on my floor, crying out of nowhere… I've just been feeling terrible, I feel betrayed. I have also been in denial, it's just so nude to wrap my head around this, and I still can't believe it sometimes, but I recently started to reach out to a few close friends, my brother, and my therapist to help me start to manoeuvre through all of this.

Unfortunately, if something this impactful were to happen to me before, my "friend" would have been the first person I turned to, and if not him, it would be my mom. My mom and I have an incredibly strong and close bond, I am very open with her about any difficulties I face, and vice versa. I'm having an insanely hard time trying to bring this up to her, but her mom instincts have clearly kicked in, as she keeps texting me and asking me if everything is okay and if I am alright. I on-line in my own apartment, but I came back home earlier this week, wanting to feel safe and hoping to talk to her about it. I want to speak to her so badly about this, but it's just a very vulnerable and embarrassing thing to bring up. I don't want to tell her that someone I've spent so much of my life with, someone she adored, did this to me, that would just make this all so much more real. I do not want to see her upset or angry. I've been debating writing out a note for her instead, because I know it'll be really very hot to say it all out loud, but I just don't know what I should even say.

I guess I'm just hoping for some support or some advice on how to go about talking to her about this, I know it will not be a pleasant conversation, but I also know she will only want to help me. I just don't know what to do, but this whole situation has already made me feel so isolated, I don't want to keep feeling so miserable and alone with this.