Could she possibly be teething??? Some molars perhaps? That would cause red cheeks, runny nose, irritable......... Just a thought.
Doesn't sound if what she ate this morning would cause it, unless she is suddenly HIGHLY allergic. My daughter was allergic to Milk, cheese, soy, and eggs. But if she ate the items cooked in other foods (ie pancakes, brownies, waffles...) she was okay. She has since grown out of the allergies, so there is hope.
Hope she is feeling better soon!
Sharon