In scenes filmed for the ITVBe reality show, Billie's co-stars attended the celebratory bash at PeaPod Cafe, which was decorated with lots of pink balloons.
The likes of Ferne McCann, Tommy Mallet, James 'Arg' Argent, Lydia Bright and Lewis Bloor celebrated the little tot's special milestone.
Nelly actually turns one tomorrow (9 July), but she had a pre-birthday party to tie in with filming. We're sure she'll be getting another special party on her big day!
Putting her recent drama with Bobby Norris, Lauren Pope and Vas J Morgan aside, Gemma was seen lighting the candles for Nelly's cake.
Billie also shared a picture of herself with Nelly yesterday, captioning the photo: "My little Nelly today in her beautiful @jamkidswear dress ... Getting excited for her 1st birthday #towie #filming xxx."
Billie welcomed Nelly with fiancé Greg Shepherd on 9 July last year making them first-time parents. Tweeting at the time of her birth, Billie said: "We are so happy and the proudest mummy and daddy in the world!"
Nelly made her screen debut alongside her mum not long after being born and she has continued to make occasional appearances in the show.
For exclusive competitions and amazing prizes visit Reveal's Facebook page NOW!
10 reasons why we want to be in TOWIE: