Who else is buried in Gertie's backyard?

Are we supposed to infer from her little comments throughout and especially from the final scene that it was Gertie herself who killed their father back in her tender teenie years? It definitely seems like there are hints that she's every bit the killer John is--only maybe a tad more discriminating. Is she reluctant to sell or rent the house because there are bodies under the flower bed? Isn't she pretty quick to break out the conveniently poisoned bottle of Irish creme when her guest becomes unruly? And she certainly has a hell of a lot of duct tape in her kitchen cabinet, don't you think?


Anyway, whatever the case, I think her performance was a real standout. She made what could have been a cartoonish character very much flesh-and-blood, with complexities aplenty, charms innumerable, and just the right hint of quiet menace. Very memorable. More Lauren German!