Allah says in the Qur’an, “They question thee (O Muhammad) concerning menstruation. Say: It is an illness, so let women alone at such times and go not in unto them till they are cleansed. And when they have purified themselves, then go in unto them as Allah hath enjoined upon you. Truly Allah loves those who turn unto Him, and loves those who have a care for cleanness.” (Al-Baqarah, 222). Thus, one should remain religiously pure to be entitled to the love of Allah for He loves those who care for cleanness and purity.
Turning to the question of problem with period of a woman, if she had a normal cycle but the bleeding lasts more than its normal period, she is then experiencing istihadah (irregular non-menstrual vaginal bleeding) and the ruling then is to refer to her regular cycle and stop praying, fasting, etc. during the time that was her regular cycle, then she should take a bath and pray, etc.
Al-Bukhari reported on the authority of ‘A’ishah (may Allah be pleased with her), that Fatimah bint Abu Hubaish asked the Prophet (peace be upon him), “I suffer from istihadah and I do not become pure; should I stop praying?” He said, “No, that is just a vein. But stop praying for the number of days that you used to menstruate, then do ghusl (take a bath) and pray.”
However, menstrual blood and non-menstrual blood (istihadah) may be distinguished by color, smell and thickness; menstrual blood is black or dark, and has an unpleasant smell, and it is thick, unlike the blood of istihadah.
May Allah guide all to what pleases him