I don't know nearly what everyone else here does, but some basics on what your little girl would have learned from her mom and littermates:
1."playbiting" is so natural, I don't think it can be eradicated but if she'd been too rough, her mom would have scruffed her. The sibling she bit would have squealed and bitten back. We "squeal" when our dogs even scrape their teeth over our hands (we don't bite back
). It's not too early to be firm about this - no spanking! - because she's got the Corgi instinct to nip.
2. Before she's had vaccines, I'm not sure how much she should be out meeting other dogs - what do all of you experts say? Socialization is critical, but she's teeny and vulnerable. Her littermates would have continued to impress on her that she's not the center of the universe, but also that other dogs are fun, not scary.
3. The best thing you can do for her is keep her growing in confidence every day. So give her lots of things to do and learn - these are smart creatures and they love challenges. Show her different surfaces to walk on, maybe a little box to crawl through, a slightly raised item to walk on and off (at her size, even a book will be an interesting challenge).
And I sure would like to see pictures, too!