Allison Williams' before-and-after make up selfie

Allison Williams with half a face of make up on. Photo / Instagram

Girls star Allison Williams has given a little insight into what it takes to get her from glum to glam.

The 27-year-old actress of the hit HBO series posted a before-and-after make-up shot on Friday, all taken in the one selfie.

Taken from the make-up chair after filming the show, the left side of her was seen with a full face of make-up, including lip liner and heavy eye make-up.

The right side however, was the more natural look, with minimal make-up, making for a very dramatic contrast.

"Took half my makeup off. Guess why Marnie might have this insane look?" she wrote on her Instagram account.

It has been a tough time for the star lately, who has postponed her wedding to entrepreneur Ricky Van Veen twice this year due to her hectic schedule and the suspension of her father, Brian Williams, from NBC's Nightly News.

Asked when she would tie the knot, the 26-year-old star said earlier this year: "You sort of think, 'What could possibly come along that would make me not think about this?'

Added: "Then current events started happening, so that derailed it a little bit ...."

Allison insists they will get married in the near future, but are still enjoying being engaged for now.

She said: "It has been this really beautiful through-line in our lives. It's just something we haven't focused on, but - spoiler alert - we are excited!"

The brunette beauty is standing by her father, whose integrity has been called into question after he admitted he'd fudged details of his coverage of the Iraq war.

She told chat show host Seth Meyers this year: "It's been tough. Obviously [it's] toughest on my dad, who bears the full burden of responsibility for it."

"One thing the experience has not done is shake my trust and belief in him as a man.

"He's a really good man. He's an honest man. He's a truthful man. He has so much integrity ... and, yes, he's a really good dad."

- Daily Mail