This is horrible, isn't it? This happened to me, and though I never knew for sure, I believe it was because the guy I was seeing at the time bad-mouthed me to her (she had initially been his friend, but she and i had become really close).
He and I were arguing on the night she blocked me, so it figures.
I recently saw that she seems to have unblocked me on WhatsApp ( I can see her profile picture, anyway). It did occur to me I could contact her, but what's the point? If she will believe my ex (who is a fucking shadester, as she would know if she had any sense) over me, then she isn't the sort of person I want in my life.....
And I don't actually miss her. On reflection I can see that there was a lot that was awful about her and her values - we really are very different people.
OP, I would assume someone may have hold her something about you - quite possibly something false or exaggerated - is that possible?
Either that or she has wanted out of the friendship for a while - is that possible? It's the mark of what a drama queen she is to block you though, if that's the case - it's absolutely possible to let a friendship fade gently, without recourse to blocking and other cruel over-blown gestures.
Either way OP, she's a selfish, immature twat. Take this as a sign to focus on and develop other friendships, with people who respect you and make you feel good, and who you fully trust. (You said she has form for this kind of ridiculous behaviour, so deep down you have known she is not a great person).
Nontheless, sorry you are going through this. It's normal to feel upset, frustrated and embarrassed, so allow yourself time to grieve the friendship.