Bethany Cox, 24, lashed out at Mark Cook after he told her to butt out of a conversation.
She threw her Black Russian cocktail in his face and smashed the pint glass in his left cheek.
Mr Cook, 29, needed 24 stitches and was left with a huge scar.
The court heard the bar had now begun a new policy of serving drinks in plastic cups after 9pm. Judge David Tremberg said Cox had “lost control”.
After the case, DC Robert Laking said: “Bethany Cox must now face the stark consequences of her violent actions.”
Last month a yob was spared jail after he viciously attacked a teen with a glass, leaving his victim with an 8cm-long scar on his face.