19" widescreen stretches text

My sister has bought a 19 inch LG widescreen monitor and I expected her to be thrilled but she says the text is all stretched horizontally.

I recall something similar happening when I first installed my Dell 21" widescreen but was able to adjust the settings to get things right, but I can't recall what I did. And without being able to see what options she is offered under display settings I'm not much use to her.

Is anyone able to suggest what my sister needs to do to get her monitor looking as it should?

Thanks in advance,
Jo

 

Thanks Ari, she's very non-techy. How would she know which is the correct resolution?