I'm so glad she has improved. Yes, keep her in isolation until at least a week after symptoms abide.
Remember the Marek's vaccine does not prevent the virus from being caught as it is a "leaky" vaccine. It merely helps prevent the tumors and lesions created by the herpes virus (which Marek's is a form of). It also does not prevent all strains of virus. A bird can still catch a different strain and show symptoms. It is hopeful that the vaccine will mitigate the damage done by the virus.
With this amount of time, I suspicion vitamin deficiency or coccidiosis.
Glad to hear she is feeling better.