I know this is a rather old topic, but I am working on a second generation story and thought it would probably be helpful to answer some question about the second generation and participate in discussion if we can get it going again.

Do you think its plausible to have her as rather confident or do you think Harry and Ginny would have kept her grounded?

I think it makes the most sense to have Lily as rather confident considering neither of her parents were extremely self-conscious. I imagine her as taking after her mother in almost every way, but she would still be her own person. She would make certain of that. I think of her as fun-loving, very independent, and free-spirited. She would also be playful and flirty with the boys, much the same way Ginny was. Lily would get very annoyed at her brothers, cousins, parents, and basically her entire family when they get protective of her, especially considering she is the youngest in not only her family, but also the youngest of the cousins. She is also very curious, which often gets her into some trouble. Because of her nature, she can be selfish since she likes to do what she wants to do when she wants to do it, even more so if someone tells her she can't or she shouldn't. Even though she doesn't normally break the rules, she isn't afraid to break them if need be. She is also recklessly brave and daring, not too mention stubborn. She is a daddy's girl, for sure, and has him wrapped around her finger. She gets into fights with her mother, though, during her teenage years since Ginny tries to have a really good mother-daughter relationship, but Lily refused to tell her mom anything or take any of her advice. I also think she'd be an amazing Quidditch player and would play as Chaser.

How do you think she would be appearance wise?

Along with acting like Ginny, I think the two of them would look very much alike as well. It was stated in the Epilogue that Lily has red hair, and I imagine it as being very long and dead straight. She would have brown eyes and tons of freckles. I think she'd be rather short, maybe not even five foot, and have a slender, athletic build.

And is it safe to say Lily and her cousins would be in Gryffindor?

Lily as a Gryffindor? Yes. And all her cousins? Um, no, not all of them. The majority I think would be, taking into consideration their parents and the environment they all grew up in, but having all the Weasley's and Potter's in the same House is a bit unrealistic and cliche.