Help with toddler clothes

So my toddler currently is in between sizes, she needs 12-18 month waists on pants but she needs the length of 24 month/2t. We recently potty trained her and she went down a size in her waist without having a diaper but with it getting colder where we live she needs to wear longer pants but none fit or they don’t cover past her mid shins. Shes 35 inches tall but only 28 pounds so she is in a weird stage even leggings don’t work because they are to short or just fall off her.