My DS also started taking off around 4. At least visibly to me. I think before that he was doing unusual things for age, but not necessarily things people would associate with a highly gifted child (like reading aloud or being socially mature). It's kind of funny. We have some close friends with a son my DS's age. Everyone who meets this child talks about sensitive and precocious he is. He is actually a MG child. He had to get access to gifted programming by the back door. Even now, it take people a while to get to the GT side of DS's personality. A piano teacher we've had for 7 months has just gotten there the past month.
And DD now 4 is the opposite. She's always loved having homework when he did and her preschool teachers rave about her and her abilities (no one was raving about DS in preschool). Anyway - I just think they're all different, in terms of personality, interests, drive, and ability. If your daughter is interested, I would definitely keep playing these kinds of games and exposing her to letters, etc. But just because she's more interested in this now, I don't think would necessarily correlate to her being more GT in the future. I think it's just natural for 2nd, 3rd, 4th, etc sibs to just do monkey-see, monkey-do and want to learn things earlier, GT or not.
