I'm sorry your friend is getting emotionally beaten up by her SO. I think if you are going to read that kind of stuff and discuss it with other friends (I assume if you all are all trying to help her, you all are all in contact one with the other and the SO is the odd man out?) you need to either back off paying that much attention, since it bothers you so but you feel you cannot do anything to help, or, if you are only reading stuff and not in actual one-on-one contact with these friends, you need to realize you may not be getting the whole story, that one of the others may have said/done something behind the scenes to the SO or your friend may have had other things going on with her SO that you are not aware of. It does not sound like any of it is about "you" so I would be careful imagining yourself included and then responding to what you imagine.

I can think about all the starving children in Africa, for example, and then get really angry at how their governments are good for nothing guerrilla thugs not caring for them but the whole is a much much more complicated scenario than that and I can't do a whole lot about world politics and weather patterns from where I am sitting, so worrying about that particular problem is an exercise in my head/imagination and getting me nowhere (toward helping the starving children or myself).

If you are only reading on Facebook, I suggest you read less often (I only go on Facebook once every couple weeks or so to catch up) and leave your emotions about what you read, alone as it is ONLY reading, you aren't experiencing the situations firsthand, do not have the complete story and might as well be getting upset about what you read in a novel?