J.C.
In my experience (skinny boys) it will only get worse until she's into the preschool years. Instead of buying smaller sizes, look for brands that have an adjustable waist and come in "slim" cuts. We had a hard time with jeans, because the fabric is unforgiving - baggy looks odd - so we've avoided them for the most part. Also, you want to make sure her pants are easy to slip on and off when she is potty trained. (no buttons, no overalls.)