Are the sizes specific to women size? Trying to buy some for my sister "Christmas" she's a size 6/1/2. Is there anyone out there who could help me?

I usually wear size 7 1/2 in women's shoes regardless of brands. I ordered size 6 for these boots and they fit just right. I am 5'4 and 135 lbs. My ankles and legs are average size for my height and weight. The boots fits snugly, meaning requiring effort to close zippers all the way to the top, for me. The boots are well made and I like them a lot, much better than other brands I tried on so I kept them. Due to the tightness for areas above the ankle, the zippers tend to open up after I get into water. But overall, for the price, it's good buy.

Would the soles protect you from reef beds?

That said you shouldn’t be stepping on the reef regardless of whether you are protected or not, the reef is not protected from you

Anyone use these for rocky shore lines? Wanting something like Japanese tabi.

I used these at Table Rock lake in Missouri. They worked great for me and my son on those dives. But i don't know what type of rocky shore line you will be on. As for these, they are not split toe, they are boots.

Does the zipper chafe the skin? How about when in fins?

I have 14 dives in them and there no chafing. There is neoprene between the zipper and your leg. The zipper stays up and is clovered by a piece of Velcro. These work great in fins. I have had no issues with these.