simivin,
First off, the world needs more people like you. You honestly seem to be looking out for the best interests and comfort of your GF. A lot of people would just take offense to their SO and blame them for their feelings. You, however, recognize that it is an issue to her. Period. And you are asking advice on how to handle. That is awesome.
Anyway, do I think you are wrong in your friendship with Sarah? No. Not at all. Your intentions are pure and you aren't trying to pull something past your GF.
I think you are addressing the whole situation perfectly. You and your GF are already talking about it and you have an idea how it makes her feel.
I don't think you will get any real solid advice from any party outside of the situation, so I will just say that I commend your handling of this and think we could all learn a lot from the selflessness in which you are approaching the problem.
You have decided that your GF is your source of 'emotional intimacy' and therefore are putting her feeling up at a high priority, maybe even to a slight detriment in your normal life operations.
Bravo man, bravo.
