Sweet Sammi, eating is a good sign!

Edit: you can download these PDFs for free, and do it on Sammi. The Feline Grimace Scale - it should help to tell you if Sammi is currently in pain. https://www.felinegrimacescale.com/

I use that, and TPR (temp, pulse rate, respiratory rate) Temp - use a rectal thermometer, temp shouldn't be above 39c. (Normal range: 37.2c - 39.2c)
Pulse rate - if she lets you, you can feel for the femoral artery underneath their back legs near the groin. Time it for 15secs and multiply by 4. No higher than 200beats per min (normal range: 160-200)
Edit: you can also use your hand under their front left leg, next to their heart if you cannot find the back leg artery
Respiratory rate - watch their breathing, when not purring! Time it over 15 seconds and then multiply by 4, shouldn't be higher than 30 breaths per minute. (Normal range: 15 - 30).

Of any of these are above their max thresholds, then Sammi may be in pain. Obviously she is unwell, but this may be helpful in the future or to anyone else unsure when to take their cat to the vet :)

Edit edit: Grimace scales seem fanciful but are used on lab mice, rats, and rabbits, cats and I believe dogs.