I have a female friend who is going through a divorce, and she will talk to me at times for emotional support. My girlfriend is not happy with this.
My friend has very few people to turn to and I do not want her to feel abandoned. Similarly, I do not have many friends and wouldn't want to lose her either.
My girlfriend, though, deserves my primary emotional attention and I shouldn't let someone else take that away. Furthermore, she feels that this sort of interaction is inappropriate and is concerned about the possibility of romantic interest arising from this, or that there already may be some on the other end. I tend to be want to help people but I don't want to be in a situation where I feel trapped by the emotional needs of someone however distressed they may be, especially at the expense of my relationship.
So, I would like to find a way to set some appropriate emotional boundaries and distance, and ideally I would like my friend to still feel supported and able to cope. Right now we do not talk too often, maybe once every week or two, but my girlfriend and I wouldn't want this to foster any dependency or grow bigger in any way.