My DS was a catnapper as well, and kinda figured it all out after about 4 months or so? I really can't remember, but the good thing was that it stopped, because it didn't leave me with much time to get stuff done before he was wailing at me again.

I know that some babies just figure it out and start doing longer sleeps, and others have to be really coached in to it, but all the kiddies that I know who have just figured it out have done so at about 4 months or so.

Good luck with it, I hope she starts getting more sleep soon. It's horrible when they wake up tired and grumpy but wont sleep any longer!