It's never too early. My mother was going through the whole process of Christmas and Santa Claus with us before we could even do more than cry and poop. lol I say introduce her as soon as possible because she'll probably discover by fifth grade that Santa isn't real, so you want to let her enjoy every year she can. Christmas becomes a bit dull for kids for awhile after they stop believing in Santa Claus, and it'll become a little dull for you, too, until she becomes a teenager and starts wanting to decorate and take Christmas into her own hands. Also, some people say that letting your kid believe in Santa is "lying". It's not lying; it's sharing in a fantasy with your kids and really helps encourage their imagination. It also makes Christmas much more fun and exciting for them.