![Smiley](https://bitcointalk.org/Smileys/default/smiley.gif)
Strange, like you're going to attempt a double spend on a few dollars at a newspaper store. Most merchants use some sort of third party service like BitPay that mitigates the risk. Cool that she's old school but she should know she doesn't need to wait all that time.
She doesn't keep people there 180 days while their credit card transaction becomes non-reversible.
How would you even manage to double spend? Don't you need to send the payments at the same time from another device? And wont the creditcard companies also mitigate the risk of a charegback? Wont they take the hit if something goes wrong or am I wrong?
Satoshi said that after a few seconds it becomes very difficult.
You would probably have to initiate a simultaneous spend on the other side of the planet and hope that the miners there find a block before the miners near the transaction find it.