The average growth rate of a kitten is 1 pound per month and Gigi appears to be going a little faster than that. But kittens often have growth spurts, so there's no telling at this point how big she'll get. If I had to guess, she'll be an average size of about 10 pounds.
Sounds like she's gonna be a BIGGGGGGG girl. Average kittens are about a pound per month of age up to 10/11 months old - then they level off.
Females generally are a little smaller, so at 4 months old she should be 4-5 lbs. Is she spayed yet? If so, you'd better watch the weight and I would not be free feeding her if you are.