Denise co-wrote and stars in Some Girl I Used To Know and last night (5 February) the audience was full for the the premiere.
Girls Aloud star Kimberley is close friends with Denise and headed down to the theatre to watch her pal in action.
Sharing a picture of herself cuddling Denise backstage, Kimberley simply said on Instagram: "#somegirliusedtoknow."
She also tweeted: "So unbelievably proud of my friend @denise_vanouten tonight she was incredible in Some Girl I Used a To Know."
After seeing her message, Denise replied: "@KimberleyJWalsh I'm so grateful to you for coming to see me last night. Thank you! Xxxxx."
It sounds like Denise's opening night was a huge success - and she has been delighted with the response.
Following her performance, she tweeted: "Alive, Blessed. Grateful. Got through it!"
Some Girl I Used To Know is set in a hotel room, with Denise acting out the entire thing. Her character Stephanie Canworth appears to have everything she wants in life, but all that changes when she is messaged on Facebook.
For more info on the show, click here!