My 1.5 year old dog suddenly has issues walking.

As said in the title my mix breed dog who is 1.5 years old has a sudden onset inability to walk, predominantly being weak in her back legs. She can walk if helped up to stand. She tried to stand up on her own, managing to get into a sitting position but then had trouble lifting her back side. She had pale gums in the morning, but the color is now pinkish.
She is very jumpy normally, but last night she didnt jump in the car like usually, shortly after we got in she vomited a small amount without much water. When she was getting out later she couldnt hold her weight on her legs and fell. We made a small circle around the house, she peed more than usual in one go, and she had a normal stool afterwards. She is usually very excited on walks and goes about exploring, but last night she was behind & by my side with no interest in exploring.

Before the evening walk, she was with me in my workshop ( tshirt painting ). Not the first time she was there, and there were no issues ever before(I probably took her there 5-6 months ago the first time). It is possible she licked / smelled something moldy as the humidity there is 50-60%.
Another thing that comes to mind is cashews. I ate some yesterday, and gave her some for the first time.

This morning she has apetite, but when I showed her a cashew nut, she smelled it showed me her teeth made a licking gesture and a slight sound, and repeated this multiple times when shown the cashew nut. We saw the vet this morning, she had no fever but he noticed her hunched posture which he said was characteristic to dogs in pain. He suggested something for her stomach ache and a pain killer, but said we could also wait a day before doing any treatment, which I chose to do.

Any opinions / suggestions are welcome.