Binos,
Are your battery charger and power cord to the computer two separate items?
ie, when you run your laptop on mains power do you run a power cord from wall to 'puter with no power "brick" in between?, which is what I read in your post. And then have a separate battery charger? Seems unusual, which is why I ask.
OTOH a more usual setup is when you run the laptop on mains power, you do it through the brick, which charges the battery in the process.
The charger for my Medion laptop (brand originates in Germany, but the hardware is made in Taiwan and is prolly common to other brands) is labelled with an input voltage RANGE of 100-240V, 50-60Hz mains freq, so it's pretty much one size fits all. The output cord to the computer is permanently fixed to the "brick". The cord between the wall socket and the brick is removable, presumably so that one can buy cords with varying plugs to suit the country you're in. At the brick end it's a standard "figure 8 on its side" two-pin arrangement.
My guess is all but the oldest of laptops would be like that. Maybe yours is too? In which case you'd only need to buy a wall to brick power cord with the correct Yankee plug at the end. Or get an adapter, as F WSYWIG says. Any labels or stickers on 'puter or brick that you can read re allowable voltage and frequency ranges?
The output voltages vary from brand to brand, so unless her hosts had the same computer Binoette probably couldn't use their brick. But then again, if they were the same and the connectors the same polarity, she could.
Cheers from the chilly south
AA