Mark Wahlberg's wife got into a bizarre war over a Beverly Hills parking spot -- and her rival even played the cancer card to shame her ... but you gotta see the twist because we're not sure who's in the wrong.
The driver of a black SUV went off on Rhea Durham ... claiming Mark's wife swooped in and stole a curbside parking spot out from under her. Once Rhea walked away, the woman told our camera guy she's a breast cancer patient, and she was trying to get to her doctor for a chemo treatment.
Watch ... the sob story does make Rhea look heartless -- until we find out why the driver was REALLY there. Let's just say it turns out she wasn't going to the doctor at that moment ... and her sympathy points are shaky at best.
Still, IF Rhea really stole the spot (there's no video proof) -- major faux pas.