What a beautiful pair of cowgirl boots!
My feet are exactly size 6 medium, but I had to return the first pair in 6 and change into 6.5. There was no way my feet can fit into size 6. The ankle is too tight that I couldn't push foot into it.no zipper. So I highly recommend you get half size up unless you have very narrow feet and ankle.
The leather was stiff when I first got them. my ankles hurt a lot when walking in them. I was too sad to return again since I really love the look, so I found a solution to soften the leather! I put them on carpet, use bare foot to step on them again and again, concentrate on the ankle part of shoes, until they become soft enough to wear comfortably. This doesn't break the shoes or affect the outlook because this leather is strong, matte and no need to look very flat. It only makes the new leather softer. Some crease may occur.  I don't recommend this procedure on patent leather or other styles that a new look is preferred.