Alright - So here is what your family friend is talking about.
Studies in the past have shown that cold water is thermogenic because the body has to "warm" the water to body temperature. However recent studies have show this not to be true. Don't really think it matters either way because it would have a minor effect.
As for water during a meal it is said to dilute the stomach acid and thus digestion is effected. Again really not a big deal either way.
Warm water will open the esophogus more and when taking things like liquid milk thistle has a small benefit.
So with all that - JUST DRINK YOUR DAMN WATER AND NOT NIT PICK.