Do you think I did anything wrong in this situation with this woman’s credit card?

My wife works in retail, and she's seen this many times, it's an obvious case of fraud. There's no way that a credit card runs into a hard limit so quickly. It was very suspicious that as soon as she bought all of that stuff at your counter, and then immediately changed her mind to return everything. It was even more suspicious that she tried to buy jewelry at the next counter. If she's worried about feeding her family why is she buying jewelry?

I agree that it was probably a stolen card.  Her initial purchases were to check that the card was valid.  After she saw that the card was valid, she had no interest in the items she had purchased, and went to the jewelry counter to purchase something expensive, that she might be able to sell on the street for cash.  At that point, the bank's computer saw that something was wrong, and denied the card.

You could have told her at the time of her original transaction that since it had been accepted as a valid charge by the card issuer, the available amount on the card will take a couple of days to correct itself. 

Anything after that is very much her problem. 

Nope, you did nothing wrong.

Credit card transactions can be voided as long as the daily batch hasn't been processed (which it wasn't).    A voided transaction (as opposed to a return) would have prevented the issue the customer experienced.

I have no clue what your employer's policies are, how their registers work or how you've been trained.    What I do know is that it was physically possible to void that transaction which you did not do.

As long as you were following your employer's policies, you did nothing wrong.   The customer sounds like a piece of work.

This is an obvious case of a stolen card, do not worry about it at all.