Incredible sudden sundowning symptoms? Something else? Help me understand what's happening to my dog

* Species: Dog
* Age: 9 years approx.
* Sex/Neuter status: Spayed female
* Breed: Pit/Cattle Dog mix
* Body weight: 53 lbs
* History: None! Routine exams, vaccinations
* Clinical signs: Pending bloodwork. No heart murmur, lungs sound clear, vision is good but slight cloudiness. No pain/pressure points, good body condition. Eating/drinking/playing as normal
* Duration: Last couple days in the evening / all evening
* Your general location: PNW
* Links to any test results, X-rays, vet reports etc. that you have: Pending!

For the last several days, around 8–9 in the evening, my dog Birdie has been having very sudden, almost sundowning-like symptoms. She seems lost, scared, uncomfortable, and confused in her own home, along with what appears to be possible vision issues. She is completely normal during the day, appears healthy and very active, and there haven’t been any major changes to her life in over 8 months.

Night 1: We awoke in the morning to find her asleep downstairs in her bed in the living room. I heard a noise that night in my half-asleep state, which, thinking back now, may have been her stumbling or falling down the stairs.

This was SUPER odd because, in the 7 years we’ve been together, Birdie has never willingly left my side. She has little to no autonomy; she won’t so much as go into a different room without me. She is a shell of herself when I’m away and won’t eat or even play with our other dog until I am back. I rescued her from a man who was abusing her and we have been connected at the hip since. Her sleeping downstairs was our first major red flag.

Night 2: We went to bed as usual. I awoke an hour later to her panting and pacing from her bed to the hallway, stopping for a moment, and then walking back to her bed. She did this 5+ times before I got up and slept with her downstairs, thinking she was overheating (it was warm).

She did not fall asleep immediately. She paced around, sniffing and looking around like she was in a brand-new place. She was panting and staring aimlessly. She would also choose the path of MOST resistance when moving around, like going over our other dog or under the coffee table, both of which I’ve NEVER seen her do.

Night 3: We were really paying attention at this point and properly freaking out. We were testing things to figure out what she was experiencing. She was again panting and seemingly staring into the void, her ears up and attentive.

When I called her to me, she would walk straight past me and look around, as if she couldn’t see me.

She fumbled up and down the stairs, with and without the lights on.

When I asked her to jump on the bed, she completely failed and fell.

When I asked her to get off the couch, it appeared as though she couldn’t tell how far the ground was. She almost “felt around” for it.

At one point, she was wagging her tail, which bumped the door behind her, and she jumped in fear—as if she wasn’t aware the door was behind her.

When I said our usual “let’s go to bed,” it appeared as though she didn’t know what that meant or where her bed was. Normally, she’d trot happily to bed.

She slept on my bed next to me this night. She would wake a few times and start panting, and I’d pet her back to sleep. I’m not sure if she was just overheating (because I was lol) or if it was part of her episode. She slept soundly and very still.

Night 4: COMPLETELY NORMAL ALL NIGHT.

No staring intently with her ears perked, no heavy panting. She went up the stairs completely normally and swiftly. She jumped on and off the bed with ease.

I took her to the vet on Day 3. They listened to her heart and lungs and felt her back and body for any areas of pressure or pain. Nothing. Her gums looked good. Her vision and depth perception seemed good, although there was slight cloudiness. No obvious signs so far.

We did a full senior panel of bloodwork and a urinalysis, and we’re still waiting for the results.

In the meantime, I’m absolutely panicking. This is my heart dog, my left arm, my whole soul. The dog I got in my twenties when I was young and dumb, but when I needed her the most. I know aging was inevitable, but so soon?? So sudden?? Will the one soul in this world who loves me the most, one day forget me? I need to understand what she is going through. I’m so scared for her.