Sizing is the problem here. Woman wears a size 8 shoe. XS is too tight (like wearing a 61/2 shoe) but small is too large (like wearing a size 9 shoe).
Fins work - be careful they make you use muscles that are rarely used.....you will be sore.

I ordered a size large because my foot size is an 11 male (US). The fins were too big. I will return them and try a smaller size...I rated the fin great, because the site made me put down a rating, however I never actually got to swim in them, becuase they were to big (wide) for my foot.

Even though I read that the product runs large and I got a size 4-6  for that reason, they are still too big to wear in the pool. I will be returning them

I just got these fins due to the need to "feel the water."  They are definately a great help!  Keeps you honest, with hip adduction and rotation, helps with the feel for ankle rotation.  Upon advice from my Masters Coach, I had been wearing socks with my regular fins.  I put socks on with these and had a great fit.  No "play", no rubbing.  If you want help with the breast kick, these are the fins!  I wear a 12 mens shoe, I got the gray 10-12 fins.  Great fit!  Worth every penny!

The fins seem to fit a little small and cut a little on the sizes by the ankle, but they do train your feet to position the right way in breaststroke kick.

Very helpful