F18 How do I handle feeling left out of my best friend’s(F18) other friend group?

I (18F) have been best friends with this girl (18F) for 10 years. We always have fun together, but it’s usually just the two of us going to the same place and talking.

While I was living abroad in Switzerland for 3 years, she met a group of friends from her school. They do exciting things together — BBQs, sleepovers, train trips to other cities, etc. Now that I’m back, I don’t have many people here, and it’s been really hard to meet new friends.

I’ve never directly asked her to introduce me to them, but I often say things like “oh, that sounds so fun” when she mentions what they do, hoping she’d get the hint. The strange thing is, she rarely talks about them at all. If she goes somewhere with them and I ask who she was with, she’ll avoid the question, change the topic, or ignore it completely.

Sometimes I feel insecure around her, like she’s “better” than me — not because I actually believe she is, but because she seems to be living a more exciting social life. It also makes me sad that she doesn’t share details about her friends with me, while I’ve always told her everything, even when I was in Switzerland.

Because of this, I’ve been feeling pretty lonely, a bit jealous, and worried she might eventually get bored of me. I’m not sure if I should talk to her about it directly, try to find new friends on my own, or just let it go.

TL;DR: My best friend has a school friend group she met while I lived abroad. They do lots of fun things together. She rarely talks about them and avoids questions about them, which makes me feel left out, lonely, and a bit jealous. Not sure if I should ask to join them or move on.