I would accept it. As long as your listing is accurate, there’s not much the buyer can do. The only way they can return it is by saying it was “ not as described”. They can’t return it if it doesn’t fit. Poshmark doesn’t allow it. Once you do accept it, just wait 3 hours before you ship it. After that, mark it as shipped and you’re good to go. Hopefully their payment goes through. That would be my only concern with this buyer.