We just do not know how to enjoy "nothingness" anymore.
Some of the best meals I've ever had were with loved ones, sharing "small plates"... some call them tapas... over a long time.. over great conversation.
We just don't get it anymore.
Food isn't best enjoyed with one hand on the steering wheel and one hand on the cell while driving. Likewise, relationships aren't best when conviently brief or cut off.
I do appreciate your question. You are conflicted. It makes sense. I get it.
I also think, when in doubt, consider your loved one first. She isn't trying to harm anyone. She takes time to enjoy her meal.
Sure... ill break the rule and get irritable when my 6 year old will diddle daddle and not eat. And then complain that his food is cold.
But here... unless there is other compelling info that's not been stated... you stand by her. So... she doesn't shovel it in like the rest of us. Good for her!
When the buddies make noise about her eating too slow, tell them that she's always been one to appreciate her life, to savor her experiences.
If they still don't get it... well... they never will and it isn't your job to make them happy.
Tend to your wife. This is not the battle to fight. Stand by her. See her side. Defend it.
Unless she intentionally disturbs your life with patient food... I just don't see how to put her to the wall for this.