A few questions:
1) Do you have other employees that work from home exclusively?
2) Do you have quantifiable measures of performance?
3) Does she have a specific measure of performance, in writing?
4) If she were actually performing up to par, would you care if she was working from home?
5) Does your employee handbook, or HR Handbook have any specific details about working from home?
6) Is there some measure that she can point to that shows that she is performing?
I am sure your atty will ask all of these. In my business, I didn't care where people worked from, as long as they performed. If they weren't performing, then there were issues.
Some owners or managers like face time. They want to see the person in the office. Doesn't have anything to do with performance, but has more to do with personal preference. You should make sure you know which one you are before you see and pay for atty fees