Hi, savvy_online, welcome to PsychCentral (PC).

I would point out how often things "go wrong" (break ups of relationships) for your loved one, not in a told-you-so way but in a factual, caring way and see if I could convince the person to try therapy to help understand why and how to change their life for the better. But if your friend cannot see it, will not believe there is a problem, then they are not likely to want to try and solve it?

Here's a good article on paranoid personality disorder: http://psychcentral.com/disorders/sx37.htm