You dodged a real hard bullet there mate.
The main errors were not even her not wearing panties on a date (though doing it on the first date is a red flag). I've had girls not wearning panties on second dates or knowing them for a while and then she deciding to fuck me and coming over without panties, but that is different than showing up to a date without panties.
I recommend reading up on rational male
https://therationalmale.com/
Huge red flags:
+ My guess she lives in the US or Brazil? US is a slut training center - both high school and even more colleges. The same American girls growing up in Germany or France would be highly different. If she grows up in Brazil, then it is only marginally better, but for different reasons.
+ her broken family - the family is already a red flag. They are at one side religious, but on the other side broken up and she gets passed around different family members - this is a huge red sign. That tells you that her family is not stable and religious (truly deeply religious couples try to make it work and rarely divorce even if they are not particularly happy with each other - they do their most to make it work). Also her religious upbringing generally has the oppositive effect on girls as we know - women who are forcibly restricted break out in rebellion. "Being bad feels sooooooo goooooood."
+ long-term relationship over distance is only temporarily possible - the average American 19yo girl is not one of them
+ a 19yo girl tells you that she moves to the Big City (Sex and The City lifestyle) and you think nothing of it?
I don't think that you could have done much frankly. You need to become smarter and more perceptive about girls - you ignored massive red flags. No amount of frame, value or Game would have helped reign in that pony over distance. The only way would be to hire 2 constant body guards who would have to tail her (and even then she would have probably attempted to fuck one or both of them).
And the best status quo would have been to not be in a LTR with her until you were living closer together. Also never ever tell girls that you like them to have notch-counts of 3 or less. The default strategy is to make the impression of being the most liberal cuck out there, who sees it as an enriching way of self-discovery when a girl fucks 100 men before you. Heck - tell her, that you would not even mind if she fucked 300 men before she was 18. That is how you find out the truth and not telling her how you like conservative low-notch count girls.
Another matter - high libido with girls is great, but you gotta watch those ones even more - observe all the signs and symptoms. And you squarely ignored them all. There are ethical high-libido girls - they just use the vibrator a lot when their men are not around - not all girls cheat.
But boy - she honestly wanted you to raise another man's kid and you would have been the paying cuck in that system. Even if you had found out later, then it would have been too late later and you would have to pay decades of child-support for another man's kid! Jeez - I agree with Serious Sam - let that marinate a bit in you. Just don't become bitter - not all women are sluts, but a lot of them are.