On the flip side, if she is in the age-appropriate class, perhaps she has little in commom with the kids in her class.

But, I completely agree with Mk13 and CCN. If she was simply stating rather than complaining, I wouldn't worry much. Most of the world is extroverted and can't imagine that it would be fine not to have any friends outside of books and God, but we introverts know that there is nothing wrong with choosing to be alone.

How do you think your DD feels about things?

She thought she could, so she did.