Bad friend?

So, I don't have many friends at school. I'm the girl who sits alone at lunch, doesn't talk in class, etc. But I've been friends with this girl Emily since fifth grade. Lately I've been noticing that's she doesn't really value me as a friend. Like every time we leave a class together and we're talking, she'll see one of her other friends and just immediately ditch me to go talk to them. She doesn't even say bye or anything, she just leaves. When we were at dorney park for a field trip, we were hanging out and then she randomly left me alone for over two hours before even bothering to look for me. Then this weekend was the last straw, when she agreed to come over on Saturday and then said she couldn't come until Sunday. I asked why, and believe it or not she made other plans with someone else. I said it wasn't nice to change plans at the last minute. She got mad, and said it didn't matter because we hadn't "officially made plans" even though she agreed to come Saturday. She said why can't she just come Sunday? I think the only reason she even wanted to come was because she wanted to play on my PS4. I said I was tired of her ditching me all the time. She just said sorry and stopped texting me. What do you guys think? Is she a bad friend?