This could be part of her problem. Chickens are flock animals.
Quarantine is very tricky for backyard chicken keepers. We generally have neither the space nor the facilities for a true quarantine.
https://www.backyardchickens.com/ar...nderestimated-part-of-raising-chickens.67097/
There's nothing wrong with grass clippings from a lawnmower unless they are excessively long to the point that they get impacted in the crop. If the lawn is cut frequently so that the clippings are only a couple inches long then they're fine.
A lawnmower that is properly maintained isn't dripping oil on the grass as it's being cut or belching heavy levels of fumes at them (If you're is, you need to have it serviced).
After all, hay is also cut by machinery that is lubricated by oil and runs on fossil fuels.