Praise be to Allaah.
This extra, non-menstrual bleeding is from a vein and is not counted as part of the regular period. A woman who knows her regular cycle should not pray, fast, touch the Mus-haf or have intercourse with her husband during the time of her period. When her period is over, then she should do ghusl and after that the rulings of women who are taahir (pure) apply to her. If she sees any blood or yellow or brownish discharge after that, then this is istihaadah (non-menstrual bleeding/discharge) and she does not have to stop praying etc.