LOL!
The old Kleenex-mantilla trick, eh? (Was your sis exaggerating? I feel sure it was a CLEAN Kleenex.)
My wife still gets apoplectic when she recalls the tissue-wearing faithful she swears she saw as a girl. There are many chapels where something close to that custom still reigns.
St. Paul was in favor of ladies covering their heads in church because "Your hair is your glory," and female beauty can be distracting to others, especially men. But Kleenex is possibly more so, judging from my wife's reaction. . .
Well, it was a crumpled up Kleenex that came out of the aunt's purse, so the "used" or "dirty" factor may have just been a matter of relativity, but in the imagination of a young girl it turned out to be quite significant.
To this day my sister becomes quite agitated and animated when discussing the issue. We have so much to laugh at from our childhood, I'm just thankful to God for giving me my wonderful parents and siblings.