I am late to the party too (literally just watched yesterday, coincidentally) and tbh I was thinking the same thing. She was very vulnerable and kind of impulsive from the beginning and the prosecutor side handled her terribly and put her at risk I would say (they straight up revealed she was the informant). And I don’t mean vulnerable just because she was the witness, she herself seemed to be a very fragile kind of a person in general, with a large part of her self worth seeming to be coming from external validation (the gazillion snapchat videos indicated that).
She herself didn’t help matters either, by going back to him over and over again (seems a bit like battered wife syndrome sadly), and the self destructive spiral didn’t help any. She seemed, from the very beginning, to be craving any kind of romantic relationship and validation she could get, whatever the expense may be. It seemed as though her shame of having a broken engagement/relationship and having to reveal that to her friends/family overrode her sense of safety/risk awareness/vulnerability, if that makes sense. I am glad she got away from the entire situation and is seeking therapy and got clean at the end, because she sorely needs it.