Given that the novel consists almost entirely of Pamela's reflections and descriptions of her personal experiences, it seems only fitting that the novel would be named, uh, Pamela. It fits in with (and helps kick off) a whole boatload of eighteenth- and nineteenth-century novels named after their female protagonists: Clarissa, Roxana, Moll Flanders, Evelina, Emma, Jane Eyre … the list goes on. By naming these novels after their characters, the authors signal that we're in for a good dose of character development, interiority, and psychological realism.
Of course, there's also Pamela's subtitle: Virtue Rewarded. No surprises here: we're set up to see Pamela as virtuous and awesome, just the kind of girl you want to take home to mom.