Best friend of 10 years dropped me. I feel lost.

After a conflicting conversation that led to a week of silence, my best friend of 10 years ended things with me due to her own reflection and realization that she is constantly feeling manipulated and guilt tripped by me. However, I’m confused because she never expressed this during our friendship.
She herself admitted that she would brush things off that bothered her. When I told her that I wish she would’ve told me about these bothersome moments in the moments that they would occur, she said she didn’t notice/have this realization about how she felt until now.

In our 10 years of being best friends, I can count on ONE hand the amount of serious conversations we have had regarding our friendship because we almost never had any. Every time I’d have an issue with something she said or did to me, I would tell her. But her? Nothing. Of course, it makes me wonder if I wasn’t paying enough attention but at the same time I don’t understand how two people can be best friends for this long and not feel comfortable enough to tell the other person when they don’t like something they did. We were practically twin sisters type of best friends but now I’m questioning the entire friendship.
I feel awful that I made her feel that way but at the same time it feels really strange that she chooses now to bring it all up instead of having brought it up in the exact moments when she felt it.
I know everyone processes things differently but this is just…i don’t know. I tried to talk it out with her and tell her how important communication is and how we need to be having serious conversations with each other when things bother us instead of brushing it off but she was firm in her decision and did not want to continue speaking. I feel so lost right now and in shock and almost like there has to be underlying things at play here.