Social Jealousy issues

I'm trying to learn more about a particular social issue (amongst a few) that I am dealing with.
My girlfriend is a very likeable person. She's exceptional at creating great rapport with people and never fails to bring a relaxing, warm energy to a social dynamic; partly why I fell for her. When we're alone it's great. When we meet one of my friends, their faces light up and the flow of conversation/ attention can become uni-directional. I at first attempt to join in but their conversational interest in each other is obvious, and I end up feeling a bit like I'm the third wheel at a date (though their interest in each other is platonic, not romantic). It's a huge blow to one's self-esteem when friends you've known for years have better rapport with someone they've met a few times than you. Kind of makes you feel like 'why do I bother'.. so I sit there silently, feeling a bit embarrassed, feel socially worthless and annoyed with my ex for ignoring me. I feel like saying "fine, be friends, I don't need you" and storming off, but of course I don't. I don't think they are actually doing anything wrong, so I don't overtly show any upset, yet I can't help feeling angry and depressed about it. I end up feeling less close to her, yet ashamed for feeling bitter.
What would help is if I could learn more about this- is it common- when I look up 'jealousy' I seem to find only stories and articles about people being romantically jealous, not platonically- what does it look like from an outsiders perspective and what can I do.

I can see why you might feel put off, but this can also be a learning opportunity where you watch "how" she makes conversation that engages others. Also, you should be proud of your girlfriend in that you found someone your friends like instead of having a girlfriend that is an embarassment and dull.

Does she ignore you? Or is she one of those people with a great affinity for people and someone with charisma? I tend to be like your girlfriend to an extent. I am very friendly and have always been able to make friends and relate to people. My husband is an introvert and I guess I am more of an extrovert. He always says I make friends for the both of us. He prefers to be the quieter of the two of us. I dont think he is jealous of me or my relationships with people but Ive never asked either. Do you think she just goes about her business with you tagging along or does she assume you are right with her but just quiet?