I need a helpful contribution, Lisa decided to have hot cocoa. She cannot drink milk and most milk products because of her lactose intolerance.

I need a helpful contribution,Lisa decided to have hot cocoa. She cannot drink milk and most milk products because of her lactose intolerance. She got some lactase enzyme (Lactaid tablets) at the local pharmacy. 

Lisa adds two Lactaid tablets to the hot milk. Her hot cocoa causes severe stomachache and she wonders why?

Why did her lactase fail to work?Use terms enzymes, denaturation, proteins, lactose, lactase...