I know a few people that have tested positive as far as FB friends. No one in my immediate family or friends have. I would presume at some point, I will know someone close to me. My sister is convinced that she had it back in November with all of the symptoms and it went on for several weeks. Of course no one knew anything about covid then.
Your sister is not alone in thinking that she may have had COVID back in November 2019. Several co-workers also believe that they had it then too.
I have had several friends and family members test POSITIVE for COVID. So far ,most of them just had mild cold like symptoms, body/bone aches. One did have a high fever which landed him in the hospital but it didn't progress to his lungs. He does get fatigued earlier in the day than he used to prior to having COVID.