do you mind if i ask how old she is?
Hi there and welcome. I never personally had this but some women have some bleeding when they ovulate. I'm not sure about 5 hours of heavy bleeding--- but some women do have some bleeding. some women have bleeding mid cycle due to hormonal responses to and it is called break through bleeding. I'm guessing she is too young to be worried about fibroids.
If she is of a certain age, I'm sure she does an annual pelvic exam and I'd just mention this to her doctor.
Bleakthrough bleeding midcycle is not unusual though. goodl uck