If the Manager's home is not an office, business or public facility it's not subject to ADA requirements. And furthermore if she is trying to go into your Manager's property without their consent it's trespassing.
Your position should be, "We don't want anyone going inside the Manager's personal residence." And if you're concerned about it set up a picnic table next to the mailboxes with a sign next to it that says, "Office."
I do remember reading an article about some handicap activists that would go around and find businesses that don't comply with the ADA and sue for fun. So consult an attorney if you're not comfortable with internet guidance or think it going to become a legal problem.