Smaller Sizing
The Pivot Mach 5.7 is available in an X-Small size that will appeal to smaller female riders between 5' - 5'5". 
This smaller size has been modified accordingly to ride well for women of this height and weight, which includes providing a lighter suspension tune, smaller head tube and a lower standover height for confident handling and a comfortable position.
If you're taller than 5'5" then no problems - you can get the Women's Specific Build on any size.

From Pivot Cycles:

"At Pivot, we believe a bike should fit the intended rider not the other way around. We build our XX-Small and X-Small sizes to fit riders from 4’11” to 5’5” and have custom tuned shock valving to match lighter riders. Our smaller sizes are built with shorter head tubes to create greater stand-over heights and we use smaller diameter tubing and a lighter, more compact frame. All of this attention to proper fit further distances Pivot from the competition, so that all Pivot frames provide the same incredible performance for every rider size. Our approach to rider size-specific geometry on our smallest frames relies on a balanced fit, and adjusted geometry to maintain correct wheelbase lengths and handling to properly accommodate the proportions of a smaller rider. Whether you’re a World Cup XC racer or simply demand a perfect fit and the best products available, you can rest assured there is a Pivot to fit you".
 

Pivot Cycles have exploded onto the mountain bike scene with incrdibly stiff and efficient dual suspension mountain bikes.