i wear a women's 7 in Nike regular shoes, but went with a 7.5 on the zoom force 1s..
People don't normally wear sneakers the same way they wear boots. Most people wear their sneakers bigger than their actual foot size. What size are your feet when you measure them against the wall or with the use of a brannock device?
It is unlikely that boots would be larger than your sneakers.
Do the 7.5 ZF fit your feet?