I think this is a difference between Portuguese and English usage. In the UK, unless we are talking about certain continental breads (not the typical case), bread is not a count noun (we use loaf/loaves for this meaning) it is simply a type of food, therefore "a little bread" can mean a small quantity of bread.
No. That needs to be either "She eats a few breads" or "She eats a little bread". The first would be quite unusual in English but there are bread items which some people call "breads", things like breadsticks, for example (individual items are typically called "loaves" or "rolls").
"Some" is quite an ambiguous word in English. In theory, it could be any quantity at all from a little to a lot, though in every-day practice it is likely to mean a quite small amount. However, I would think "Ela come pão" is more suited as a translation to "she eats some bread", and "Ela come um pouco de pão" to "She eats a little bread".