Usually with most of the external parasites-you will have flashing due to them trying to scrape them off and itching.
Lymphocystis is a virus and will not respond to medications-it has to run its course-Usually it will grow-split open-ooze-drop spores that other fish can either pick up or infect other fish if they have an opening from a wound
and repeat that process-It can take 6weeks to 6mo. When it splits open you do have to prevent secondary infection due to the open wound-Usually an extra water change over and above your regular water change and good nutrition is all that is needed. I would keep her in QT until it runs its course.
IMO-I would avoid the copper based products in your display tank due to the long term effect.