You wrote, She made a big deal out of it and even mentioned it to me during and afer the break break up, as some kind of huge sacrifice she made for me.
So she remained in some kind of "poly" or "open" relationship mindset, that is more troubling than even her past.
And she had sex with you at the same time as two other guys were you aware of that, with all the STD risk it put you at.
She promised she would only have sex exlusively with me from the get go. I also asked her about stds before having sex and she told me she was clean because she had a test done recently.
But you are right otherwise, i could not have been sure of her claims and promises but i decided to take my chances. I have decided to take an std test soon. I do not think she had sex with anyone else in the meanwhile because we pretty much spent every night and most days together from the first date so her opportunites to do that were slim but not impossible. I didn't knew her for very long so i never trusted her words to the 100%.
Aso you are quite right about her mindset. after the break up she told me to call her anytime for casual sex and i became somewhat angry given that it was the very reason why i left her.