What do you mean by the phrase "as long as its not too long" in your response, "just have her add water to the reservoir as long as its not too long." Whats too long?
Also, in the old days one should always wait to let the engine cool because removing the cap could release steam risking a burn. Is the VW coolant system under pressure when its hot? I ask this because the white reservoir appears to be plastic so maybe pressure is not as big a deal??