There is nothing wrong with a woman whose period has ended putting on the clothes that she was wearing whilst menstruating, so long as they are still clean and pure and none of the menstrual blood got on them.
But if some of the menstrual blood got onto the clothes, then the place where it is must be washed before praying in them. A woman came to the Prophet (peace and blessings of Allaah be upon him) and said: Menstrual blood may get onto the clothes of any one of us; what should she do with it? He said: “She should scratch it, then rub it with water, then wash it, then pray in it.” Narrated by al-Bukhaari (227) and Muslim (291).
So the Messenger of Allaah (peace and blessings of Allaah be upon him) enjoined purifying the clothes before praying in them.
And Allaah knows best.