The feisty singer gave as good as she got, however – telling the Directioners: "Niall is my home boy… won't take abuse from u" and added the hashtag "justfriends" to clarify their relationship.
Tulisa and Niall were attending Rochelle Humes' Disney-themed fancy dress party when the photo which worked the fans up into a frenzy was taken. The shot showed Niall – dressed as Prince Charming – leaning Tulisa back, as if he was about to give her a Disney-style kiss.
She captioned the image: "As If my little muffin turned up as Prince Charming looooool #bruddafromanothermother."
The brunette had transformed herself into a princess for the do – which was and attended by the majority of Rochelle's fellow the Saturdays band members and their other halves, who really went all out with their costumes.
Tulisa posted several other snaps from Rochelle's belated 25th birthday party. In another she can be seen with HELLO! Online blogger Una Foden – who made a very convincing Ariel from The Little Mermaid.
Birthday girl Rochelle chose to dress up as Princess Jasmine, while her husband showed off his buff physique in a tiny waistcoat as he took the role of Aladdin.
Elsewhere, Vanessa White dressed up as Esmeralda from The Hunchback of Notre Dame while her boyfriend Gary Salter came as Captain Hook.
Also opting for a pirate-inspired costumes was mum-of-one Frankie Sandford who went as Pirates of the Caribbean's Angelica while her footballer fiancé Wayne Bridge dressed as the Mad Hatter.