Well, I did it while putting together a poster as one gigantic Powerpoint slide (greatest idea ever in using the HDTV for a monitor for this). I used my mini-DVI to VGA adapter on my MacBook to hook it into the VGA port of my HDTV. Change ports as needed, but I bet you can go VGA-VGA, DVI-DVI, mini-DVI-DVI, DVI-VGA, mini-DVI-VGA, or DVI-HDMI depending on what exactly is used on her laptop.
My Sony HDTV has a PC video connector on the back as does a friends Toshiba. My HP note book PC has a HDMI output which would match up with the HDMI connector on the TV. Does her PC have a blue connector with an icon that looks like a little CRT? If it does that where the video output is.
Short answer is Yes, you can. It just comes down to cabling, the instructions for the laptop and the tv will advise on which variant will be best.
I’d guess the TV-out socket (DIN socket) to composite video in.
I think screen burn is only a concern when the same image is displayed for hours upon hours. Probably nothing to worry about for what the OP’s wife is doing.
S-Video cables cannot carry an HD signal. If you have an HDTV and are using S-Video cables you have seriously gimped the television.
You need HDMI, DVI or Component (Y, Pr, Pb) cables depending on what your TV accepts to get the good HDTV stuff.
Note: Do not buy cables at your local Best Buy or such stores. They are an absolute ripoff there. There are many internet sources which will sell them for a fraction of the cost (just did a quick check…Best Buy Monster Component Cables = $80, Internet = $10).