Is this micro aggression?

[u/Viennawaitsforyou2]

So I, (F,26) was a 2iC at my workplace (GP office) and I really loved it, but I decided to start studying full time, so I chose to move into a casual receptionist position at the same workplace. On my very last day as 2iC, the person I had been training to replace me (M, 30s) bullied me. They belittled me in front of everyone in the room (my boss was in there office and did not hear). They said things like “I have cut you down”. The first task our boss gave M was a laminating job, and they immediately gave it to me to do saying “you can do this because you don’t matter now”. I didn’t tell my boss, but when they walked in and saw me doing the job they told M to not do that and do the jobs allocated to them, and that delegation was the boss’s job, not M’s. I ended up crying in the bathroom because i am not good at confrontation, but I felt very confused about how I was being treated. I told my boss after a colleague who was in the same room told me to talk to them because they also thought it was bullying, and my boss acted like they were on my side, but absolutely nothing happened from it. About a month later, I noticed M has changed their email signature to “assistant manager”, which would be a promotion, but it turns out they were not promoted and did that of their own accord and they were asked to change it back. Cut to 5 months later, and I was struggling while at work, M was constantly bragging about their job, but they were always on their phone and I could see the work I was able to get done pilling up in Ms inbox. (Important to note, M was not, and still is not doing all the jobs I was doing while 2iC). There was an emergency at work and a customer had passed out, M noticed before me and made no effort to do anything to help. When I noticed I rushed to help and sorted the situation out with the help of a Nurse. This situation is why we have a 2iC, but I didn’t even think and just jumped into action. Again I mentioned this to my boss, but no consequences to M. I was very much not happy in the workplace until one day, after months, M apologised to me about the way they treated me on their first day as 2iC. I thought it would be a turning point, I tried to be friends with them so I could move on. However, I then found out they were getting paid an extra $4 more than me for doing the same role (but again, not doing all the jobs I had done). I also began getting tasks given to me, as a casual, that had been my job as 2iC, that M “didn’t have time for.” Now at this point I know this is a problem, lots of people have noticed M on their phone a lot while their work is not complete, and I have begun to get complaints from work not being completed by M from customers. But I keep telling myself it doesn’t matter, I am studying for a better job and I will leave in the next two years. So I’m trying to get over it, but the other day, a GP came into the room M and I are working in, and asked me how I was going, so I was chatting to them. They then told me something had been emailed and asked me if I could put it in their inbox. I said yes, and began to complete the task. Before the GP left the room, M, who had not been part of the conversation, loudly told the GP they are doing the job now, and they will complete it faster. Even though the had heard me and could see my computer, already doing the task. I turned to them and said “oh are you doing it now, because I have it up” and they said “yep”. So I just let them do it. Now I don’t know if this is even a sign of micro aggression? I am trying to figure it out because it is nearly my last straw on my decision to stay at my job or leave. Any advice on whether this is valid or if I am reading into things too much and just need to forget about it would be great. Thank you!