I have not used it before, but could it be the doming resin she is using. Someone else on here mentioned that you can get it at Rio Grande.
That particular one looks beveled, so she may have used a mold for that part. Put in resin, let it set, brush a little onto the picture and put it on top (carefully so air doesn't get trapped), then put down the tile. Someone somewhere in this forum had mentioned something about creating doming effect with embossing powder, so that may also be something to look into. But um, if you're using resin, what's the point of using scrabble tiles (instead of more resin)?