Do recurring dreams of being chased by jinn and devils, along with reading the Quran to expel them, and hearing strange sounds in the house, indicate the presence of a spiritual affliction (mass) even though the one experiencing this is diligent in her prayers?

These frightening visions are caused by Satan and do not indicate demonic possession. The cure for them is to maintain the remembrance of Allah before sleep (adhkar al-nawm) and recite them contemplatively. If a person sees something he dislikes, he should: seek refuge with Allah from Satan and the evil of the vision, spit lightly to his left three times, turn over to his other side, pray, and not speak about it. There is no harm in seeking out a reciter for Ruqyah (definition) Shariah.