I checked the U.S. State Dept site for visa info. Here's what it says:
"ENTRY/EXIT REQUIREMENTS: Travelers to Morocco must have a valid passport. Visas are not required for American tourists traveling to Morocco for fewer than 90 days."

I think the real question is: Can she get through passport control, get into town, and see anything then get back to the airport and through whatever tangle of lines there are within the 5 hour time span?
Debra