hello Sam,
this happened to me last Thursday. I knew I had read a thread or two about the subject, so searched for what I was looking for, check out thread,
there are some interesting posts
it may not give you the answer how long do I wait which was my question too. I sent my first email to the customer 5 hours after the Folksy notification, but I had no answer, I then emailed her again 23hrs later, (see thread above) and then 25hrs after the initial contact I cancelled the order. I think if you email the customer at 9amish, time shops open and ask her if she is willing to reorder.
As you say , it has been the weekend, and she may have been busy, but you have a business to run and as long as that item is in her basket it is not in your shop and nobody else can see it thus not order it .
Hope you get a positive result
Suzzie x