If it was truly square, wouldn't you want 1024 by 1024?

Not that it is an option or anything, I wonder why that is.

So, any ways, assuming the cabling is snug at both ends (monitor info indicated only one cable type, D-Sub) with her PC as is, the only other thing to do is play with the actual monitor's settings, upgrade motherboard BIOS, or try different driver versions.

On-board video though on desktops is generally awful on older PCs.

Of course the other option is a new monitor, here at least, they have gotten so cheap for 21"/22" Widescreens, that is where I would start.