Sizing cuff

[CJ57]

I’m at my wit’s end so bear with me!
I have a customer in the US who has decided this Christmas that his wife wants a cuff like those worn in Schitt’s Creek. Never seen it but you can buy cheap copies on Etsy and I sort of wish they would.
They have picked a couple of mine but getting her size to see if either are suitable is driving me to distraction with nightly emails and blurry pics. She doesn’t appear to have a bracelet/cuff of her own and I’ve even suggest they go to a shop and try some on for fit.
I’ve had photos of a hand and a tape measure and tonight he has found a piece of wire which he has formed into a bracelet measuring 22 cm. that seems very wide as her wrist measurement appears in the pic to be a bit over 6 3/4 in. No idea how wide the wire is and as one of mine is concave and 1in wide and the other is concave to tapered about 3/4 in wide I’ve no idea how this translates
I have a really narrow wrist so cuffs don’t work well and I’ve always sold direct to customer after they’ve tried them all on. I’ve tried talking them out of it but he’s determined so how do we get an accurate measurement? Neither of mine are soldered so there is a bit of spring.