Will offer this for consideration - simply because I have one extremely similar but smaller and in tones of brown tiles. It was a cottage industry/tourist souvenir from Mexico. Many talented craftspeople whose identities will never be known. Decorative value - yes; monetary value - not very much.

As a fairly serious mosaicist, I agree with duluth. I will also say that if your friend really likes mosaics, there's a *world* of art mosaic, both present and past, that awaits her discovery! I can offer links if you're interested.