Woman spotting during the days of her period due to using the pill

If after the 7 days, she still experiences spotting, then she should wait as this can be part of her haiz (since it is within 10 days). She should not perform any salaah in this time.

If the bleeding or spotting stops within the 10 days, then this will be her new haiz habit. However, if the bleeding or spotting continues after 10 days, then she will revert to her previous haiz habit (i.e. 7 days) and she will regard the spotting or bleeding after the seventh day to be istihaaza. She will have to perform all her missed salaah in the period of istihaazah.

And Allah Ta'ala (الله تعالى) knows best.