She was out in Bev Hills showing off a lot of cleavage, and even more of her ridiculously hot legs ... just hours after reports came out she's separating from her husband.

She did lunch with a table full of friends. There was champagne on the table -- so maybe the gathering was more celebratory than somber. The ex 'Real Housewives' star and husband Romain Zago reportedly separated in December.

If looking good is the best revenge, Zago just got punched in the throat.

Then again, this is just what Joanna does.