All the laptops I've ever destroyed have a metal plate as foundation of the keyboard; the necessity for stiffness controls. As a rule, minor spills don't get past the keyboard module and its baseplate. That's not hard and fast. If the spill was on an edge, liquid may have leaked past.

Disassemble machine, remove keyboard, being careful to pop the cam on the flat cable connector rather than just pulling it out. If you don't know what I mean, look at the connector. There's a plastic bit attached to the board, with a flange or lip running around it; if you pry up on the flange, it pops up and releases the cable.

Distilled water + Isopropanol (alcool isopropilico) + a trifle of dishwashing detergent. Soak, slosh, then rinse, first in distilled water, then in isopropanol. The purpose of the isopropanol rinse is to get as much of the water out as possible. Allow to dry thoroughly (overnight in a dry place, at least). Yes, you can buy isopropanol in Mexico. Easier than here, in fact.

If the keyboard's recoverable, that'll do it. If not, you haven't lost much.

If she's in Mexico City, she should go downtown to the shopping district off the Zocalo. Face the government buildings, rotate 180 degrees, walk about three blocks... in that area she'll find any number of stores selling computer gear of all kinds. Somewhere in there she'll find somebody who'll replace the keyboard for her for not much money. Sorry I don't know the names; the shops come and go. There are other places, of course, but not so easy to find.