Who is Donna DeLuca from Kissing Doorknobs and what is their importance?

Tara's eighth grade friend, Donna DeLuca, has had an operation that required a needle to be inserted into her eye. She seems a bit rougher than Tara, but they have similar senses of humor and get along very well. Tara tags along with Donna on her dates and worries about her getting pregnant, which she ends up doing anyway.