The pretty fitness trainer shared a black-and-white photo of herself kissing former cage fighter Alex Reid, with her hand held up to the camera to show off her sparkling engagement ring.
In the snapshot, Nikki had scrawled the words"I said yes!" onto her palm.
The personal trainer captioned the image: "[I'm shocked] he finally asked me I'm officially going to be Mrs Reid!"
She also uploaded a photo of her first congratulations present to Instagram, too, writing: "It's all happening!"
And, just in case any wedding planners fancied taking on the couple's nuptials, Nikki also shared a close-up of her engagement ring, writing: "[Wedding planners, we] need help ASAP please email Alex Reid's PA nikki@alexreid.co contact him on @alexreid on Twitter."
The hint seemed to work reasonably quickly, as excited bride-to-be Nikki later announced that her wedding planner was "exhausted" with all the plans.
ALEX REID REACHES OUT TO DAVID MCINTOSH IN OPEN LETTER
The muscle man, who found fame after becoming Katie Price's second husband, confessed on Twitter earlier this year that he had found love with the pretty brunette.
The 37-year-old posted on his Twitter account: "Ok guys, it's official, I love @fitnessbird xxx."
Nikki also proclaimed her love for Alex on her Twitter feed, saying: "Can't wait to see my amazing bf and get away from London xxx. @AlexReid love u xXx."
KATIE PRICE'S LOVE LIFE IN PICTURES
Alex has a 10-month-old daughter Dolly with Chantelle, whose relationship famously turned nasty when she accused her ex of having a sex dungeon.
Before that, his marriage to Katie - aka Jordan - lasted a mere 11 months.
Let's hope Alex really has found 'The One' this time - and congratulations to the happy couple.