This is the nature of ME/CFS (caused by Covid or otherwise), it does vary somewhat over time although the course is not always to improvement or around the same level but sometimes to death. She received some form of experimental treatments in order to gain the prior recovery which was at least a stellate ganglion block, she has not mentioned what else she may have received.
Hopefully she maintains a higher baseline from here on out and the production of these videos doesn't produce further Post Exertional Mailise that could worsen her condition.
Many different viral infections and other immune pressures can kick off ME/CFS. We don't yet know what otherwise actually means really, Epstein Bar Virus and Influenza but there is likely many others and only 70% of patients with the condition say it was initiated with an infection. Its a question well worth good research, there just isn't much in the way of funding for ME/CFS.
Hopefully she maintains a higher baseline from here on out and the production of these videos doesn't produce further Post Exertional Mailise that could worsen her condition.