What poison can be put into milk that doesn’t make it taste horrible yet kills like that? Cyanide? How would she have gotten her hands on that?
Remeber this is Pakistan where goat milk is the norm, and refrigeration is unheard of. Warm, spoiled, goat milk probably tastes so bad that any poison would be easily masked — heck, it might even improve the flavor.
"Inquiring minds want to know?"