bleeding 3 weeks after her period?

Hi,
Welcome to ehealthforum,
If the bleeding is normal, it could signify early periods. If bleeding is lighter and shorter it could suggest possibility of late ovulation, breakthrough bleeding, possible implantation bleed. Chances of pregnancy cannot be ruled out if you were sexually active after her last periods (and if you are not using any form of birth control). Wait and watch for her periods. Look out for development of any new symptoms. She should consider visiting her doctor/gynecologist for further evaluation to look for the underlying cause. Treatment as appropriate would be started based on examination and investigation results to help her.
Take care.