How do I deal with my coworker?

I started a new job about 6 months ago. My boss is also new and started at the same time I did and I have one other coworker who has been with the company for many years. Initially things started off great with my coworker, they were friendly and helpful. I mostly shadowed this person for a whole month which involved attending meetings. I would just listen in. One month into my role something changed, without any communication, they stopped inviting me to meetings. We also had a backlog, which initially I was told we would both work on but it just ended up being me. I was okay with that because I looked at it as training. Then they asked me to help out another team with their backlog and train someone from another team, which I also did.

I noticed that my own training had halted a bit and so I brought that up and we set up some training sessions. During training, my coworker would QA my work but I noticed they were making changes to it and the quality of my work was actually going down instead of up. I wasn't sure if it was intentional. I confronted them about it and we aligned on a few things but following that I was told that only one of us should be in each meeting and since I am new, it was always her attending these meetings and telling me what work needed to be done. Lately, it has started to feel like I work for my coworker, they are delegating work to me, constantly criticizing everything I do and basically told me that I should run everything by them before doing it.