Acorn Women's Slouch Boot Slipper

I wear a woman's 6.5 shoe. Should I get smalll (5-6) or medium (6.5-7.5)? Thanks

Do these have any arch support?

I wear a 9 1/2 sometimes a 10. can't decide on l or xl?

i would normally wear a size 12 in womens, would the X-Large still fit me? i dont have an acorn store anywhere near mw to try them on.