<human>: Can you condense the text into three sentences or less?

I realized this after a story my mother told me about the prior Christmas. My uncle's wife told everyone she wanted to do all the work for cooking and whatnot, instead of having my elderly grandmother do it as she usually does. This was wonderful of her, but she needed to make sure she made most of it without any milk products as my mother is lactose intolerant among other milk allergies.

Now this should have been no problem at all, as it is surprisingly easy to make most foods without milk with little taste change. That, and she did not need to make everything without milk, just a few things so my mother could eat too. It is important to note that she also holds a Master's degree in Education, something that is not particularly easy to obtain. It is assumed it takes a significant amount of intelligence to reach this, and one would also assume at least slight attention to detail when someone's health is involved.

On the day of, my mother checked with her and asked if she had in fact made certain things without milk. She replied yes. 

My mother asked, "So what did you use instead?"

She replied, "Margarine of course, it doesn't contain milk."

Suffice to say, my mother did not eat much that Christmas.

(And yes, some margarines do not contain milk, but most do, and this one certainly did as clearly marked on the label.)
<bot>: My uncle's wife with a master's degree in education does not know how to check labels for milk before cooking and my mother resorted to eating almost nothing for Christmas dinner.