You kinda have to be direct. Hints seem to almost never work. Believe it or not people can be quite oblivious to those things. Also many times when your in a situation like this, the hints you think your sending out also tend to be less direct then you think they are because of your own hesitance to do it directly and somewhat hoping they don't find out.
As for feeling like a scumbag. Yeah it would suck and the guy might get upset, but it's not like it really is a scumbag move.
Sure if you just wanted to sleep with her or something it would be a scumbag move, but in this kind of circumstance it's completly understandable (or would be for the guy down the line.)
I mean seriously what are you supposed to do, just be depressed and lonely the rest of your life with no resolution? Anyone can understand that eventually i'd think.
Besides, if she leaves him after 4 years, I think it'd be a sign that it wasn't going to work out anyway.
