💔 Found out my best friend has been talking behind my back for years, still processing it

Have been close with this friend since our school days, close enough that I genuinely considered her one of maybe two people I would call in any real emergency without hesitation. Last month, through a mutual friend who let something slip almost accidentally during a completely unrelated conversation, I found out she has apparently been making fairly unflattering comments about me to a wider group for what sounds like years, not dramatic betrayals exactly, but small, consistent digs about my choices, my relationships, things I had actually confided in her directly and privately over the years. Confronted her about it directly, and she first denied it entirely, then eventually admitted to some of it while downplaying it as just normal venting that everyone apparently does about their close friends occasionally, framing it as something universal rather than something specifically hurtful in our particular case given how much I had actually trusted her with over the years we have known each other. What makes this specifically harder to process is that our friendship otherwise felt completely genuine on a daily basis, she showed up for me during real difficulties more than once, remembered small details about my life that most people would not bother to, which makes this discovery feel less like uncovering one clean lie and more like realizing two somewhat contradictory things about the exact same person can apparently coexist simultaneously. We have not fully cut contact, mostly out of genuine uncertainty on my part about what I actually want going forward rather than any clear decision made yet, but every interaction since finding out has felt noticeably different, more guarded on my end than it ever used to be before this specific discovery happened. Part of me wonders if I am overreacting to something that, as she claims, happens in most long friendships to some extent, and part of me feels like the actual betrayal is real regardless of how common something like this apparently is among other people's friendships generally. Has anyone navigated discovering something like this about a genuinely close friend, and did the friendship actually survive in any real, meaningful form afterward, or does something like this usually mark the beginning of the actual end?