Well, it looks like congee is the same thing that Aunt Bea posted: http://www.thaifoodandtravel.com/recipes/congee.html
jabbur, it looks like there are different variations of this soup/porridge - sometimes it's cooked longer so the rice grains breaks down more, which would make it more white.
Can you ask her to write down her mother's method in English? Writing it down would prompt her to think it through more than describing it verbally.
Or maybe her mom could write it in Thai and your friend could translate.