However you notice them getting more and more arrogant the more you talk to them.
One day you're talking to them like normal, they find out something about you; something that's quite obviously personal to you and you're going to be sensitive about it. But being the socially retarded person they are, they go on and on about it, making fun of you for it, even when you show signs of being clearly pissed off.
Even when you tell them to shut the fuck up and go fuck themselves, tell them they've gone too far and to drop it, they'll use the little piece of information they have against you in retort, to piss you off further.
I swear to fucking god, I'm not impressed.
However in that instance when she tried to blackmail me i bet her to the punch and cut her shit out of my life.
At least, if your TRYING to look on the brightside you now know this person now isnt trustworthy and you shouldnt give this person any information that can be later used against you.
Hope things work out in your favour whether ye stay mates or not.