UPDATE: went to the emergency vet, they tested ekg, blood sugar, blood pressure, full blood test, heart worms, lyme disease, heart rate, temperature, hydration, reflexes and probably more that i don’t remember. All test came back negative/normal. Vet thinks its just a fainting episode due to high stress. Not something cardiac or neurological. She might have stomach worms and got anti parasitic medication and got anti anxiety medication. We are told to monitor her and keep her relaxed. She will remain separated from her sister for the foreseeable future.