Actually, once initiating a descent (with the cabin set to airport field evelavtion and the pressurization mode in descent) the cabin altitude will decrease gradually to the field elevation. During this time, the cabin differential pressure decreases, but remains above 0 - meaning there is more pressure inside the cabin than outside.

If there wasn't any cabin pressure in a plane below 9,000 ft, the differential would be 0 PSI and the internal cabin pressure would equal the outside air pressure. The cabin altitude would then descend at the same rate as the aircraft itself. Most pressurization systems are set to descend at around 300 ft/min to maintain passenger comfort. But pilots frequently descend at rates of up to (and exceeding) 2,000 ft/min on approach and landing. This would make descent very uncomfortable and potentially painful (especially for those with sinus congestion or respiratory problems).

Further... with plug type doors or over wing exits (as described in this scenario where the door has to be pulled in and turned before it can be opened outward) the differential pressure ranges anywhere from 0 PSI on the ground to over 8 PSI at cruise. A typical exit door, say 48" wide by 84" tall has an area of 4,032 square inches. With just 1.0 PSI inside the cabin, that's over 4,000 pounds of pressure holding the door closed. Unlikely a 52 yr old woman could manage that...