The couple, which met on the set of 2005 movie `Pride & Prejudice`, decided to end its five-year relationship shortly before Christmas, according to the actress` father Will.
But Knightley has refused to wallow in self-pity at home and hit the streets of London for a night of sing-along fun with friends, including her `The Edge of Love` co-star Miller, reported a daily.
The group showed off their vocal skills on tracks such as Queen`s `Don`t Stop Me Now` and Bon Jovi`s `Livin` On A Prayer` while drinking Cosmopolitan cocktails at the Lucky Voice karaoke bar.
"It was a pretty raucous affair. The girls went really crazy for Cosmopolitans. They weren`t holding back at all. There were about 12 people in the group, but no diva-like antics. They all got stuck in (involved)," said a source.