So, these guys are homies to me for 8 years. They are in LTR for 1.5 year and 2 years. I have met both of their LTRs. By the description of their daily behaviour and how my homies have to deal with them on daily basis, it seems these girls definitely have BPD. I am 200% sure of it. We are 18 year olds. I don't want my so close friends to ruin their youth on this "the one" girl they have found.
I can't just point them to askTRP. But, I also can't see them in such suffering that they have to keep up with bullshit of their "GFs".
Physically they are in very good shape.

When I ask them to let's go to bars and bring girls home, usually I have to go alone. And they never act on IOIs, they don't approach and say to me, "I have one girl, why would date other?" What the fuck dude is my reaction. How do I just fucking let them know that this mentality they have is just gonna fuck them up in very near future.

One friend is also even considering to LDR her. I feel bad because they are my friends after all.

Enlighten me, elders of TRP.