TIFU by fixing my own toilet and flooding my downstairs neighbor

I noticed a small leak under my toilet last Sunday and decided to fix it myself instead of hiring a plumber. I watched a couple of short videos and thought it was just a loose seal

I shut off the water supply and removed the base of the toilet to replace the wax ring. I picked up a cheap ring from the hardware store and figured it would do the job. After reinstalling the toilet I turned the valve back on and tested the flush. Everything looked dry so I went to bed feeling proud that I saved a few hundred dollars.

At midnight I heard a dripping sound and discovered water seeping through the floor into the ceiling of the apartment below. I scrambled to place towels under the leak and shut off the water again but the damage was already done. By morning my downstairs neighbor had water stains on her ceiling and her living room carpet was soaked. She was furious that she woke up to a wet couch and half her electronics damaged. I offered to cover repair costs and pay for a plumber but she said this was more than an accident. She is now demanding I find temporary storage for her furniture and wants a written promise to fix everything

I feel terrible and overwhelmed by the mess I created and the stress of dealing with insurance claims and contractors. TIFU

TL;DR:
I tried to fix a leaky toilet myself installed the seal incorrectly and flooded my downstairs neighbor’s apartment leaving me on the hook for major repairs