Why must they grow up so fast??

My sweet little Abby is 15 months old now. She's a tiny 20 lbs 10 oz and 29 inches. She is so beautiful it just takes my breath away sometimes! She is looking and acting more and more like a little girl and less like a baby. It's bitter sweet. I love seeing her learn and develop, but I am sad that her baby days are rapidly dissolving. She is speaking in sentences (both verbally and in sign) and to this point I have lost count of all of her words. She LOVES to color and of course, read. She sometimes like to play with her blocks and build, but mostly she likes mommy to build and she plays Abbyzilla. She thinks it is hilarious.