When is too much?

It was 6th grade and I had no friends, that was when I met Emily. Emily’s group was small and was willing to accept me. But no one clicked better than Emily and I and out of that group only her and I are still friends. In 6th grade all the way up to 8th, we had the best friendship. We believed in all the same things, had similar up-bringings, and were interested in all of the same things. When we reached our freshmen year of high school, our friendship took a detour. She and I were simply just interested in different things. We both joined sports and activities that took up all of our time. We had no classes together and we didn’t even have lunch together. We both made new friends and didn’t honestly reach out to one another much. The summer after freshman year we rekindled our lost friendship and was good as new. By the time junior year came around things changed. She started to really want the attention of the popular girls in our grade (I had no desire to be friends with these girls as they had been my bullies in junior high: and Emily even knew that). I blew it off and just thought “she is her own person and can make friends with whomever she pleases”. Although if roles were reversed I wouldn’t become friends with her bullies (but that’s a different conversation). She began to say and post things that I knew she didn’t stand for or believe. If anyone would know her, it would be me. It was frustrating because she was gaining this popularity by saying things that I knew she didn’t actually mean or stand behind. (I am not a jealous friend btw. I didn’t care if everyone loved her of if she she was popular. I just didn’t want her to change herself to get there). So I made a new friend. Emily was ditching me and I needed someone true. So I met, let’s say “Adam”. She HATED Adam. She put up with him being around because she knew he was my best friend but did not like him, and she told me on multiple occasions. But nevertheless she made a new friend herself, “Monica”. I equally did not like this Monica. Monica was not kind. She was blunt and rude and was emotionally and mentally taxing on Emily. Even Emily didn’t want the friendship anymore at times but like Emily, I put up with this new Monica. But a year passes and she ends the friendship with Monica. Although I didn’t have any problem with Monica (yes she was a bad friend to Emily but other than that I didn’t have any drama with her and could have been friendly) I still decided to have Emily’s back. I did not talk to Monica or even be friend her on social media because she had done my “best friend” wrong. After high school ended Adam and I had a HUGE falling out. It was BAD. It honestly took months to get used to not having him around. But unlike how I acted when Emily and Monica ended, Emily decided to hang out with Adam the DAY we had the falling out. Emily made sure to post a photo of her and Adam together. Note this day I was devastated I lost my best friend and to see my other best friend acting so buddy buddy with Adam hurt! How could Emily hang out with him on today of all days after years of hating him? I took a break from talking to any of them for months. Eventually I hung out with Emily once more. While hanging with her she gets a call from Adam and a text. When I looked over Adam had sent a picture of me, mocking the photo, to Emily!!! Why would he send that unless they have done this before, was my thought. It also made no sense since I had Adam blocked from all my social media’s. So Adam had another friend screenshot my photos. Which is weird. To this day Emily is still buddy buddy with Adam and is very public about it. Constantly posting photos or even text messages between them. I guess I’m confused on what I do now. When the roles were reversed I chose to have her back and to ignore Monica so why didn’t she do the same If we are truly “best friends”??? This isn’t the first time Emily has been weird either. Do I just drop her? It’s so hard since we’ve been friends for over 10 years. Any advice?