
Originally Posted by
luckychris
I agree with the response you received from cas, but I'd like to add to it a little.
"Lying on the bed" refers primarily to someone's physical location/position at a point in time. The subject could be napping, reading, working, watching television, etc. When someone is "in bed", it usually implies that the bed is a major part of the purpose of the person's being there. She is or was sleeping, or is ill, depressed, or has some other reason closely associated with that item of furniture.