@Heya it depends on if every cycle is that long or if it keeps changing, some may have a period for 3 days and some for a month but if it's normal it's probably fine but if it's a sudden or slow change then they should definitely see a doctor
@Heya Girl for me it lasted 2 weeks and it's always been like that, it can be inherited from the family or you're simply born like this, but to be safe, she should go for a check-up