I'm sorry to inform you, but a demon isn't leting you forget about your friend, it's really a demon inpersinating her/him. People some times see angels, or they can feel god, but they can also see demons, and feel demons. it all depends on what the circumstance is the feeling that you get or what you've been doing. Ex: if you've been playing wiht a Oujhi board, then it's PROBABLY demonic, actually for certain it is, seance or tarot cards and such, not good.
A friend of mine felt a huge weight on her once, and she had just been reading a book about demons, she prayed and told the demons to go away, (god says you have the power to do that if you're one of his.) and they did, she felt lighter, and the room actually got brighter.
She also had a dream where something was attacking her, and when she woke up, she was screaming and sat bolt upright and ya, demons again.
So while people have also seen angels protectig them, or some thing, demons are what ghosts and spirits really are. and even if you say a goast was praying with you, remember that demons can even quote the bible, they have nothing agains pretending to pray.