Update time.
My mom is much, MUCH better, and it turns out Christmas was a culmination of a series of seemingly coincidental events that were actually all related.
So a couple weeks ago, she caught a cold. However, the cough never subsided. This is not too unusual, and she has had a chronic cough since 2009, and was in fact already seeing a pulmonologist about it, who said it might be asthma and gave her an inhaler. However, the cough that happened after the cold was unusual in that she would cough so much she would throw up and had shortness of breath, which had never happened to her before.
A few days before Christmas, she took a fall when chasing a dog out of our yard, but she felt fine after.
On Christmas, my dad came to visit and help prep the turkey. Part way through the morning, her ankles and wrists (mostly ankles) swelled up to the point where she couldn't walk, and she started throwing up. After her holding out for a while, Dad finally convinced her to go to the docs and drove her to the hospital. I joined them later.
Mom and I (dad left to run some errands) spent 6+ hours first in Urgent Care, then in the actual ER. The long and short of it is that the cold she had triggered her lung shit as well as some kind of dormant arthritis that caused her system to start attacking the minor injuries in her joints, turning it into bigger injuries. The way the doc put it was, "your body thinks the best way to get rid of the minor injury in your ankles is to get rid of your ankles."
She's got steroids now, and she's been sashaying around the house now that it doesn't hurt to walk anymore.
Thank you to everyone who expressed their concern and well wishes! I hope everyone had a far less eventful Christmas than we did.