There is an anti fungal that you used to be able to get. @casportpony likely knows the name and status.
You would have to figure out which infection is more critical and tread it first.
Euthanasia is also an option
I do not see where you posted her age. Mareks tumors start at about two years old but can start earier. They usually have tumors inside as well as outside and they are usually diagnosed upon death
https://www.backyardchickens.com/articles/the-great-big-giant-mareks-disease-faq.66077/
It is good to have someone double check. I once gave dosing advice based on an average large fowl weight to someone that had a bantam! I was lucky in two ways: first was that they caught it and secondly they do not bug me for chicken advice any more!
:lau