What if a disability accommodation might cause morale problems with other employees?

Q. An employee whose doctor says she cannot stand for long periods of time recently requested an accommodation. The employee requested the opportunity to sit on a stool while she works. We are concerned that giving this employee a stool will prompt other employees to request seats of their own, even though they do not have the disability she does. Do we have to accommodate her request, knowing that it could lead to significant morale problems?