I have two questions regarding Nifas the first one is: a sister who just gave birth and after 8 days she is almost clean and says she has a little line or spots of brown blood. She wants to know if she has to take a bath and pray or wait 40 days?The second one is: if she is clean before 40 days is she allowed to have intercourse with her husband?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

As a rule, there is no clearly defined for the minimum period of time for confinement bleeding. So, when bleeding comes to an end and a woman finds purity (free from traces of bleeding), then she has to perform Salah and observe fasting and it becomes lawful for her husband to have sex with her.
Imam al-Tirmizi said: 'There is agreement among Muslim scholars that a woman in her confinement should give up performing prayers for forty days unless she finds herself pure (free from traces of bleeding) before such a period of time, then she has to perform Ghusl (complete ritual bath) and perform prayers.
If she finds blood after forty days, she is not allowed to give up performing prayers according the majority of scholars' .
Anyway, if she becomes pure before forty days and then she finds blood again and recognizes that such a blood is related to confinement due to its smell and color, then she has to give up performing prayers and observing fast, and it is Haram to have sex. But, if blood has no indication that it is a form of confinement bleeding, then she is pure and has to do what other pure women do.
Allah knows best.