I suggested that she turns on a radio really loud in the attic. Since they travel by sound waves I would think it would drive them crazy and just move out. I know they are our friends, so I don't want her to kill them. When bats live in the walls or attics of buildings, their noises, odour and parasites create problems for people. Bats, however, are beneficial mammals that feed on night-flying insects such as moths, mosquitoes and beetles.
Bats are an important part of our ecology.
One Little Brown bat can eat as many as 500-600 mosquitoes an hour for a total of two to five thousand a night. A colony of bats can eat hundreds of thousands of mosquitoes a night. Bat control should be limited to excluding bats from buildings.