What is the interpretation of visions in Istikhara, and do bad visions have a connection to Satan? Is seeing the deceased in a dream true, and is there a connection between Istikhara and visions?

What a Muslim sees in their dream could be a vision from the Most Merciful, a dream from Satan, or a self-discourse. These visions are not necessarily linked to Istikhara, as the result of Istikhara is seen in the presence or absence of success (Tawfeeq). If the girl has repented and become a person of faith and good character, then proceed with the matter. There is no harm in repeating Istikhara, and Allah will destine what is good for you.