I bought my mother-in-laws car two months ago. It had 12K miles on it, so you can see she didn't go far with it.

I don't think so. Was the oil changed? If the oil is dirty or thick it would do that.

Take a look a this site, for one:  http://www.pistonslap.com/ My 2002 Camaro sounds like a diesel engine when it's cold.  It has never been a real mechanical problem, just loud and a little annoying.

That sure sounds like my engine.

125K and counting on my '94 Grand Am

The 5.7 liters in the Camaros do the same thing. We noticed on the Camaro police interceptors, 1998-2002, that they knocked when cold. The dealership always referred to piston slap.  GM kept saying they were going to a new piston. Since the Camaros were discontinued after 2002 we never followed up on the problem. These cars still went over 100k miles and were still running when we took them out of service.

GM 6 CYL have always been noisy. Lotsa valve tappet noise. Ya might wanna pull the valve cover when the weather warms up and make sure its pumping oil nicely through the push tubes to the rocker arms. If G-ma just puttered around with the Jiffy Lube Quaker State in it then it may be a lil gummy.
You could run maybe a quart of Risoline or another cleaner additive in it for a couple of weeks and then change the oil to see if that helps quite it down / clean up the motor.
Bright side is the GM 6 CYL is one of the most resilliant motors on the face of the earth. They take a lickin an keep on tickin... Tuxblacray2007-03-17 06:06:12

Slick 50...

And yeah, you can expect a little slap in da morning on just about anything GM has put out for the last 20 years.
Mama's '85 has been doing it since we've had it.
Can you say "Heche en Meheco"? The GM bean-counters sure can...
If your noise IS p-slap, you shouldn't have any worries, as long as you don't have a flashback, and believe you are Barney Oldfield...

Sometimes I think I'm Barney Oldfield... does that mean I'm going to have problems down the road? 

Depends on what road you go down...
Besides...thinking it, and believing it are two different situations...