Is there anything upon her after she purified, and then her husband had intercourse with her, and then the menstrual blood came down again?

You bear no sin for having intercourse with your husband, because the intercourse occurred during a valid period of purity. The purity between two bleeds is a valid purity, during which a woman is obligated by what obligates pure women, and her husband is permitted to have intercourse with her. A woman recognizes the cessation of menstruation by seeing the white discharge (al-Qassah al-Bayda') or dryness (al-Jufūf), not by seeing a brownish discharge (al-Kudrah). The brownish discharge and yellowish discharge (as-Sufrah) are considered menstruation if they occur during the menstrual period; otherwise, they are considered irregular bleeding (istihādah). If a woman sees purity by one of its two signs, she must hasten to perform ghusl (ritual bath), and it is not permissible for her to delay the ghusl until the time of prayer expires. As for blood that returns after its cessation, it has detailed rulings.