Well you had a boyfriend, emphasis on had- he was a major dick head when you got further into the relationship so you had no way of knowing he would be like that, but as lucky would have it, just when you were gonna leave he cheated on you with some other girl and left you for her, and though you were quite happy to be rid of him.. you started feeling bad for that girl cuz she doesn't know what shes getting into.. so while its probably not a good idea cuz its technically "non of your business" you decide to find her and warn her before its too late... you pulled some fbi shit (ofc-) and found her place, now you just gotta go warn her.