I probably would not bother separating her since they were all probably exposed at the same time, and she has been with them lately. If she were more severely ill, I would. Tylan injectable given orally, has a 1 day egg withdrawal after it is completed. If giving by injection, the withdrawal time would be 7 days. Tylan can cause muscle damage at the injection site (it doesn’t always happen, but possible)so I would give it orally. Here is some reading about MG:
http://extension.umd.edu/sites/exte... Mycoplasma gallisepticum (MG) Infecti....pdf
http://extension.umd.edu/sites/exte... Mycoplasma gallisepticum (MG) Infecti....pdf