Not being invited to a party - also a venting session

Hi guys!
Something's been under my skin for the past few months.
So, there's this group of friends I eat lunch with every day, and I'm like the only guy. One of the girl's had a 16th birthday party over the summer, and literally everyone was invited to it BUT me. Our group of lunch friends were invited, plus most of the entire grade. People she doesn't even like and regularly talks trash about (the popular clique-y group) was also invited as well as a bunch of other friends I have.

So basically all my good/best friends were invited, as well as the popular kids in the school, and I was basically left out. I thought me and her were relatively good friends, like we never had fights or anything, but I don't really know now. EDIT: However, now that I remember, last year I overheard her and some popular guy snickering about me behind my back

Should I mention anything to her? I was planning to talk to another one of my friends about it, should I do that?

Thanks!