What does the Bible say about people who see dead people? I have a friend who sees people who have passed away. She can see, hear, and talk to them. This isn't fake, she really can. She recently told me that she sees my deceased grandfather at our ball games. She cannot see her mother who died a few years ago, which frustrates her. She isn't religious. Does the Bible say anything about this? Is this absolutely impossible? What does this mean about the people she sees, like my grandfather? Some would say that he hasn't crossed over into the after world. I'm almost positive he was saved though. Thanks.
I'm sorry to have to tell you this, but the bible calls this necromancy and describes it as an "abominable practice":  


  Deuteronomy 18:9-12 (ESV): 9 “When you come into the land that the Lord your God is giving you, you shall not learn to follow the abominable practices of those nations. 10 There shall not be found among you anyone who burns his son or his daughter as an offering, anyone who practices divination or tells fortunes or interprets omens, or a sorcerer 11 or a charmer or a medium or a necromancer or one who inquires of the dead, 12 for whoever does these things is an abomination to the Lord. And because of these abominations the Lord your God is driving them out before you. [emphasis mine]


To inquire of the dead is to intentionally initiate this activity, and a medium is someone who engages in necromancy professionally.

Unfortunately, your friend's experiences are most likely due to the influence of a demonic spirit as per the slave girl in Phillipi. Her visions and conversations may seem very real to her and she may even receive special knowledge that she would not have access to through natural means. This doesn't mean that she is really seeing dead people however - demons can and do deceive people about such matters.  I suggest you seek pastoral counsel for the best way to help her.