I'm sorry that you had to experience this💕 I've also had asimilar experiences as this but one stuck with me in particular although it wasn't even that bad, but still- Once in 9th grade (it was around the end of the school day so there weren't many people left) I was talking with one of my friends and I had a pretty good time with him, just laughing and talking about nonsense like we always did. Then after a while a girl from class joins into our conversation which I didn't mind cause she's usually very friendly and open minded - at least from my perspective. In the middle of talking with them I suddenly stuttered at the beginning of a word and out of now where she started to mimic my stutter and chuckled afterwards - twice. I was really caught of guard by this and after that I stayed pretty silence the rest of the conversation. I don't know why it affected me so much but I guess it's because I became more and more comfortable around other people and definitely wasn't expecting it. Now in 11th grade and being again in the same class as her I was able to forgive her it since I'm pretty sure that it wasn't with any malicious intent but I do sometimes get reminded of that situation when I talk with her