What is the average weight for a 5'1up female 18 year old?

Wow!Almost anything! There's a huge variation of normal sizes for an 18 year old girl...Genetically predetermined; although nutritional intake may modify this. Go to the website "www.Cdc.Gov"; type "growth charts" in the search box in the right upper corner of this webpage; click thru the menus until see appropriate chart for 18 yr-old girls. The 50th %tile could be considered "average"--but normal is 5th-85th %tile.