Why would you want to know.
R3v1D here i have been watching alot of Extra Halo content and i see that in 3 cases Kelly "spartan 087" is always about 1 1/3 smaller then Master Chief . Chief is 7' 2.3" tall so my best guess will be that she is 6'2"- 6' flat or so . Hope this helps for something i think she is pretty cool happy to see her in the game :)
Pic 1 is from Halo 4: Forward Unto Dawn - Part 5 (Live-Action Halo Series)Pic 2 is from the game Halo 4