Does she want them back, otherwise it's none of her business. Sometimes things like being relocated can cause enough stress to get existing problems to show themselves. I really think your other birds will be fine. I know what it's like to watch something go down hill and not being able to do...
I'll share my experience with Mareks, I bought some chicks from tractor supply and some from a swap meet years ago, a couple in each group developed Mareks, we culled when it was obvious and they were symptomatic. For me, it seemed to be self limited to those couple of birds, the few that never...