i know there are folks on "both sides" but i think you made the right call here (sorry was a couple pages late on reading your initial story).
here was someone who was willing to throw away your "friendship" over a trump-adjacent "doctor" and her crazy opinion. she clearly had not vetted this person, because that's not what these people do. they latch onto something they barely know anything about, then defend it to the teeth against any and all comers. like you said, trump was not brought up, and she was the one who instigated the break in friendship (social media, or otherwise). if this was the hill she was willing to die on, then she needed to die on that hill.
there was an article posted a couple months ago about "how do we reason with people who disagree with us (trump people)". the takeaway was that often these people lash out against those who try to reason with them, and this makes them hold more strongly the crazy beliefs you're trying to untangle with simple logic and facts. by trying to have a rational conversation with her (or others) you're just as likely to make her more resilient in her beliefs. so in this case, given your history, i say fuck it, you made the right call. with any luck, she'll examine her own ideas and opinions, and the nature with which she wields them, and wake the fuck up. if she cannot do this on her own, all the calm words in the world wouldn't make her permanently change her mind.
it's a real shame, because i feel like we're all having moments like this. i have one really good friend in particular, and we have a 30+ year friendship. and he's one of these "trump is a child and he's terrible but he's goo with the economy and biden is in bed with china and aoc and hunter and spying on campaigns and blah blah". once i hear those buzzwords, i know that i can either change the subject, or put our friendship in jeopardy. i typically change the subject. when we mature, we can see how conversations are going to end before they start. i see it when i'm writing scripts. i know how a conversation that starts in the garage next to a wrecked car on page 12 is going to end on page 15. i know the emotions involved, and i know how each character is going to feel when it's over. i'm 11 years older than my wife, and it's very clear that i play out the conversations we have before i start them, and she doesn't. it's something you grow into.
in my case, with my good friend, we both know it's better to avoid getting to the boiling point. but in your case, it sounds like this was the best remedy. people like her can be dealt with with some tough love and personal time to stew on it, or with calming, logical words. if you're not that close to her, the first option is the best option. sure, in a perfect world, ideas would win out. facts would win out. but we're in a world where we can't even agree to what constitutes a fucking fact. and that's the really depressing part of this. that's a problem now, and that will still be a problem on november 4th. and it's a problem without a solution. this isn't like lord of the rings where one thing dies and everything controlled by it kinda disappears (i only saw it once, i don't really like that genre).
we need to win in november and win big. we need to make sure the reasonable people in all of our lives vote. that is more than enough. send them videos made by dems and never-trumpers. send them silly trump tweets and unedited videos. make them angry. show them what is happening in down-ballot races, house and senate, and how truly terrible some of these people are (i just read the perdue story with the anti-semitic ad). put it in front of them, and shame them if you have to.
not everyone can be saved. you wanna save someone, save yourself, and go from there.