FMLA - Physical Therapy

I need some help! We have an employee who is on an intermittent family medical leave. Her physician completed a certification in August that identified the need for this employee to miss work at any point without prior notice when her condition flares up. He has also listed physical therapy 3 - 5 times a week. In February, I was provided with information that proved this employee was abusing her FML and she was disciplined under our attendance policy for not having sick hours to cover her absences that were not FML related. At this time I also requested another certifiaction from her physician and it was completed and returned. The new certification is now listing physical therapy 5 - 10 times a week depending on how she feels. The employee was scheduling her physical therapy after work but has now requested that she use FML hours to do this during work. Her shift ends at 3:30 pm. Do we have the right to tell her that she cannot take off work and that she should schedule her appointments after work? Our other question is can we request the employee to give us specific times, dates, and the length of her physical therapy appointments to verify that she isn't abusing her FML again?