She's testing you!
I think she just didn't make it in time to get to the litterbox and wouldn't pee under the bed since this is one of her sleeping spots. She peed in the sink - but she doesn't actually sleep IN the sink, but go try to figure why she did that! And I'd take it as a good sign if she charged out of there like her back side was on fire, and also that she went down the steps on her own. At least she had the energy to do it!
It's stange, but it does sound like she's looking for something, but what? I still have the feeling that it's her advancing age and perhaps some senility that's behind all of it, but I'm no doctor!
Be that as it may, the crew here is still in her corner and saying prayers that things will improve - for BOTH of you!