Might be lace but I doubt it, if it is a laced glove and not skin then it's quite badly drawn and that seems unlikely what with the quality the art has had so far (and for it to be badly drawn three times in one (non-comedy) chapter is exceedingly unlikely), then there's the fact that there's like a 99% chance that woman was an Oni and she seemingly purposefully sent our sweet Sadako into berseker mode whilst being very happy about doing so.
There's a couple pieces of Human furniture and clothing (yes, Human as in the material it's made of) preserved and displayed in a few museums IIRC and there's pics online. You can also buy some of the pieces too but most of them are fake Halloween things cuz it's quite restrictive to legally (yes you can legally do this) produce and sell items made from Human materials that are non-medical.
Plus also basic psychology (people are fucked in the head and can quite casually do messed up shit like make Human/Witch skin gloves when they don't think of the person in question as a person) and context clues in the behaviour of the characters the last few chapters when it comes to Oni and "liberated" Witches.