i ride that same frame and it feels just right, but im like 5ft5 and 120lbs.
i used to ride a 21tt haro, too big for me, i couldnt pull that thing up, had a hard time trying hang 5s cause the frame just wouldnt pop up.... you could try a 19.5 even 20, i felt that 21 was way to big for me, maybe something that size would fit you well