Why is it so hard to trust people?

ok yesterday my cosuin who i ahev been cool with and trusted all my life was trying to set me up.she met this guy and there together now and they 3 wayed me.she was actin like he wasnt on the line but i kne he was bcus she never calls me at that time,so i lied and said i had a line but i muted them.and as thay were on mute he told her to set me up and get something out of me.im not gonna say what but it was none of his business.its like hes changing her and controlling her and shes dum enuff to go for it.and hes armenian armenian guys tend to be like that.very controlling.i feel like crap.they put me down.i need some info.my whole days mest up and im the kind of person whos very sensitive.