CCTV footage, please, Mr Starbucks. You can blank out the faces of innocent customers.
Luna has certainly committed one untruth in the "bid to set the record straight" when Luna said the customer wouldn't accept that she couldn't pay by cash - Vanessa had already paid, otherwise the dispute about the refund wouldn't have arisen. If she's paid, then she's accepted the policy. At worst Vanessa may have said it was a stupid policy - I've done the same myself, but obviously it's not the staff to blame, but that doesn't mean that people don't comment on it.
I was also wondering what was on the floor behind Luna - wondered if it was Vanessa's order, that Luna refused to supply despite it being paid for. May not be, of course. Maybe Luna regularly throws stuff around.