The women are gay or bisexual and are looking at your friend, not you.
Umm, no, LOL! I have seen women looking at her though and I do know the difference.
I'ts hard to explain by post. Just one quick example we're sitting at an event, she's on my right. To the right of her are two females. When she's turned toward me one keeps staring, and I mean long deep stare, right into my eyes. Hard to explain but from that angle she couldn't look at my friend's face. And she keeps doing this through the night. My friend caught it eventually and gave her a long stare at one point.
Believe me this is more common than you may know. I have seen women who don't even notice that other women do this. My friend is very aware and does catch it. I may misjudge it but if I were on the receiving end I wouldn't appreciate it. I can't say it happens as much with women I date. Meaning I see men sometimes look at a girlfriend but they'll stop or it's a more normal quick thing.