It was said very literally a couple of times during this fight that Alice is lacking (regarding this particular theme) some crucial experience Souma has due to his setting and circumstances while growing up. Alice apparently didn't really know what a bento is, aside from having seen pictures and read about it. So, she only got the superficial aspects of it, preparing an excellent meal but not an excellent bento. She clearly deserved to lose this time, and not because of Souma's plot armor, just like Archie expressed it.

Man, as much as I enjoy seeing the bishoujo's foodgasm faces, and whole bodies, these old men were also damn funny.

I hope Souma actually goes and asks for some of her food later. It might give him more ideas, considering his old man's restaurant certainly wouldn't have such refined molecular gastronomy. I'm sure she would enjoy serving him any food.