generally rentals are very aware and dont care if the dude is married..and normally would not blink an eye, once told the wife or gf is coming..

it's the one that became "in her eyes" the one this guy is gonna be with for his time here..

most likely he was less-than truthful...

so when she hears that he is married or has a gf, she lashes out the only way she can...tell the wife/gf of his infidelity...

it is a very tricky situation..