Best way to guestimate is take the size at 12 weeks and double it and that's your size full grown.
How old is she now? There are also ways so figure it out at a younger age but I will have to look that up for you on a YT search. You are so lucky with a little girl! I have some good things going up around the end of December. Some ne stuff just isn't available until then! I am always so tempted to dress Chewy up like a girl...I don't think he would ever know the difference!
