Broody Bantam with bad idea
I have struggled with the same problem so many times before. We have a silkie that is always willing to move nests. However, all our other hens (who aren't silkies) won't move without a fight or being broken-up. They don't like changes to their nest in the least. However, your hen may be different. I've had many broody hens break-up after being disturbed, so if you want her eggs to hatch and you don't have an incubator to use then it may be best to try to leave her be.
As for the ants, if they are a problem in your barn, there are ways to control that are safe to use around chicks. Because of the climate where I live we don't have ant problems. However, mites do sometimes get on broody hens and their chicks and a good dust bathing sight will clear them up in a few days.
I hope this helps. Best of luck!