Is my girlfriend flirting with my friend?

Anonymous
I hang out with my girlfriend and my bestfriend in a group of 3 quite often. My friend is the 3rd wheel, but my girlfriend and I enjoy his company and it's not a burden.

I know for a fact that my girlfriend's loyal and really into me and even, at times, is kinda clingy. But lately I've been noticing that she's been hovering around him more often... like if we all walk in a group, I'll walk ahead cuz I guess I just kinda walk fast... but I'll look behind and see that they haven't caught up and are making conversation/laughing as they walk at their own pace.

My friend's not a threatening dude, and I know he's not the type of guy to make any advances on her. He's actually quite silly and at times hard to take seriously, even for her... but he's funny, he's a fun dude who adds to the group's energy. I'm just not sure if my girlfriend is subconsciously flirting with him or if she's trying to make me jealous.

What should I even do in this situation? Do I hold her hand and lead her so she keeps up?

Should I even address it, or just leave it? And how do I do so without coming across insecure?
Is my girlfriend flirting with my friend?
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