In this case it means to show that you have money. The women are happy to show their wealth and pay for the break.
"Flashing" in this usage just means "displaying."
This is probably a phrase of American origin — all Americans would understand what you meant if you used it. I don't know if other countries use this phrase.
If you have a question about the English language and would like to ask one of our many English teachers and language experts, please click the button below to let us know: