'Hollywood Hillbillies' Mema -- Co-Star's Fiancee ... Good in the Kitchen, a Whore in Bed

'Hollywood Hillbillies' star, David Weintraub, just lassoed quite the Southern belle ... according to fellow star, Mema. Weintraub popped the question over the weekend to Mallory Knighton ... and gave her a 3 carat diamond engagement ring worth…