What do I do - she says she doesn't like me?

I'm a teenager and I have quite a large group of friends. One member, for the last year or so, has been making indications along with another friend that she doesn't like me. I found out that she has been holding a grudge against me for something I said stupidly years ago when we were 12 - something like "sometimes you need to be a better friend". I thought she had gotten over it but apparently she has been holding this grudge for years. Since then she has been making subtle hints such as always taking the opposite side in an argument I'm in, even if she is being very hypocritical, or I am blatantly right, or even if it means agreeing with someone she hates more than me. She also says regularly now that she doesn't like me, and will not hug me, but I took little notice as we all make comments like that in our friendship group. As we are not a touchy-feely soppy group I have dismissed this for a while, although I did feel a bit hurt when on her last day of school (she left for the summer to go on a camp) she passionately hugged every other member of our group but not me. As I know that making fun of me is a running joke in our friendship group, I took little notice, but a couple of hours after we were all home from school, she tagged me in a picture on social media, with the caption reading something along the lines of: "had the best year with friend A, friend B etc." and tagged in the 'friend A, friend B' part of the caption of the picture every single one of our friendship group (even the girl that no one really likes and the ones that don't have social media) except me. It seems like such a trivial problem but it has really hurt me and I don't know whether to brush it off or take it as it seems. No one else in our friendship group is paying attention to it and I am very paranoid now that they are all talking about me behind my back. I still want to remain friends with her as she is more popular in our group than me and has more sway over the group than I do. I don't know what to do, whether I should confront her or ignore it.