Infatuated with friend of my girlfriend

So here's a sticky situation I am finding myself in. I didn't want to make the subject title too long, but to clarify my girlfriend hs a good friend who has another friend that I think I am infatuated with. Let's call her Girl C. Now what makes this more complicated is I've never met Girl C before and have only seen her in group pictures with my girlfriend's friend.

There's something about Girl C that if I wasn't currently going out with my girlfriend, I would have inquired about her long ago. There are times where I can easily brush it off, but there are other times where I feel like I want to get to know her, but for allll I know Girl C could have a boyfriend already or she could be totally incompatible personality wise.

I feel like I'm going crazy. I know it's not fair to my girlfriend if I have feelings for someone else, but at the same time how can I know if an infatuation is short lived if I know nothing about Girl C and no real way of finding out without saying "Hey can your friend introduce me to Girl C?"

Should I just leave the lid on pandora's box?

Yes, leave the lid on...if you and your girlfriend split...well ask her friend for "Advice" and see if you can somehow meet with "girl C"

But as long as your relationship with your gf is going well, keep it so. No relationship's stability is worth sacrificing over a stupid little infatuation.

This happens, it would be impossible for anyone not to find other people intresting now and again. The core of this element is that even if this happens your conviction that you are better off with your current girlfriend should be stronger than your need to explore your options with Girl C.

Yeah,why screwing up a good relationship for something that can be disappointing .