The Touch singer, 28, took to Instagram on Thursday to announce her engagement to the footballer, also 28, after he proposed on their four-year anniversary.
And during an appearance on her bandmate's new MTV show Served! With Jade Thirlwall, Leigh-Anne revealed how Andre pulled out all the stops for the big moment, setting up an outdoor cinema and playing her a romantic personalised film.
Recalling her fateful evening, Leigh-Anne said: '[Andre] basically set up this outdoor cinema, so there was a walkway of fairy lights and candles and I was like, "this is a bit much for an anniversary, what's going on here?"
'So we started watching a film, and then halfway through it cut out and our song started playing, and then there were videos and pictures of us and there was this book on the screen that said, "four years and forever counting", and it kept opening up with pictures of us and stuff.'
'And then it just said, "Will you marry me?" and he was on one knee,' Leigh-Anne continued, as she admitted that recounting the moment was making her emotional.
In announcing their engagement on Instagram last week, sportsman Gray posed alongside his fiancée as she showed off her diamond engagement ring shortly after accepting his proposal.
He added the caption: 'Let the caption speak for itself this time... Hasta la muerte.'
Shortly after, Leigh-Anne commented on the news herself, writing: 'Guys.. wtf has just happened... He bloody did it, and I said yes...
'I'm marrying my soul mate, the man of my flipping dreams... I am lost for words, so I think I'm just going to go cry some more @andregray_ I love you so much. My world is literally complete'.
The couple, who started dating in 2016, will marry after the Watford striker stunned Leigh-Anne by getting down on one knee during their anniversary celebration.
In a second image shared with his 120,000 followers, the singer was seen covering her face in disbelief as he presents her with the ring.
Jesy Nelson, Leigh-Anne's Little Mix bandmate, was among the first to respond to the happy news, commenting: 'Congrats you beauties.'
Hours earlier, Leigh-Anne had shared an old picture of the pair kissing on a beach, but didn't mention the engagement.
She wrote: 'Happy Anniversary baby... how has 4 years gone so fast! all I know is I'm another year more crazy about you. I couldn't love you harder if I tried (sic).'
The 28-year-old singer recently admitted she was hoping Andre, also 28, might pop the question one day.
Quizzed on whether she would like to marry the Watford striker during an Instagram Live with her fans, she said: 'I really hope so. I'm just waiting, you know. I'm waiting ... patiently.'
But in April, Leigh-Anne admitted her hopes of a proposal and then summer wedding appeared to have been dashed because of the coronavirus pandemic.
Addressing the issue during a recent radio interview, she said: 'The wedding is probably not going to happen now because we can't go anywhere.
'He's probably not going to (want to) do it in the house. So it looks like my dream is officially over.
'I've not really been planning it but every girl has got the idea of what they want, we'll see, it is a dream of mine.'
Leigh-Anne also thanked her partner for putting up with her after admitting she has been unhappy with the restrictive lockdown measures put in place during the global coronavirus health crisis.
Taking to Instagram, she wrote: 'I've been a moody b***h lately with this whole quarantine thing I'm not going to lie... thank you Andre for putting up with my face all day every day.'
Foreshadowing her happy news, Leigh-Anne recently played the ultimate prank on Perrie Edwards by pretending she was engaged while co-hosting Jimmy Hill's slot on Capital Radio.
Perrie asked: 'So, is there any exciting news? Do you have any secret projects or gossip you would like to share?', with Leigh-Anne cheekily replying: 'Well it's funny you mention that...'
The brunette hen quickly flashed her left hand up to the camera as if she was showing off a new engagement ring, stating: 'I was going to tell you guys in person, but I couldn't wait.'
Leigh-Anne previously dated Ashford Town FC footballer Jordan Kiffin for four years before the couple separated in 2016.
She has also been romantically linked with Cover Drive bassist Jamar Harding.
© Associated Newspapers Ltd.