Karrueche Tran -- She's a Lady ... When It Comes to Chris Brown

EXCLUSIVE

Our photog gave Karrueche Tran plenty of chances to rip her ex Chris Brown to shreds last night ... but she took the high road each time.

We got Karrueche walking into 1 OAK in West Hollywood where our guy peppered her with questions -- asking her about jail, his alleged cheating, his new modeling agency -- all designed to get her to trash CB ... but she did not take the bait. Not once.

As TMZ first reported, Tran broke things off with Brown before word got out he'd hooked up with a girl at rehab.