A friend of mine claimed that she has seen a demon in a physical form. I thought they can still possess unbelievers today, but not appear as a physical form to people on earth. Can they show up in a physical form?

I'm surprised that, whenever this subject comes up, I haven't seen anyone point to scripture describing what demons and the devil looks like. However, I know that the Gospel of Mark talked about demons possessing humans and pigs, and Jesus being tempted by the devil. Someone replied to my comment asking my friend to clarify that she meant she's seen a physical demon, saying that 75% of people react like that to someone who is confident of their faith. So does that mean those who strongly believe in Jesus will have experiences like this? I don't feel comfortable having conversations where people can't point to scripture confirming their experiences.