AITAH telling my coworker to stop delegating her tasks to me because she thinks I finish things faster

There is a coworker at my job who constantly complains that work is piling up for her. She started asking if I could help her with small tasks. At first I did a few because we work in the same section and I thought teamwork mattered. Then she began handing entire assignments to me while saying I was better at time management so it made sense for me to handle everything. Last week she placed a stack of documents on my desk without asking and thanked me in advance for finishing them. I told her I already had my own workload and I would not complete hers. She looked offended and said she believed in efficiency and that I was blocking productivity. She then told our supervisor that I refused to help the team. Thankfully he knew what was going on because he saw the piles on my desk. Now she avoids me and tells others I made her look lazy aitah?