Can we deduct hourly FMLA leave for exempt staff?

Q. We have an exempt administrative employee who is on intermittent FMLA leave. She’s unable to work on Fridays for two or three hours due to a serious health condition. By policy, she must use any accrued sick leave when she is out sick, typically in whole-day increments. Can we charge her sick time in hourly intervals because she is utilizing FMLA intermittent leave even if we charge her in larger blocks when she is just plain sick?