The Paralympic gold medalist competed in the BBC One tournament last year alongside Nikita Kuzmin, who will face Layton Williams in the final tonight.
Ellie posted an Instagram photo of a tube coming out of her arm and connected up to a drip on Saturday, just hours before the season finale of Strictly Come Dancing.
She wrote: ‘Never would of thought spent days in December and lead up to Christmas in hospital.’
Ellie, 29, went on to express her appreciation to the NHS personnel who had cared for her.
The retired swimmer was the sixth celebrity evicted from Strictly last year, which saw Hamza Yassin and Jowita Pryzstal win the glitterball trophy.
Soon after her departure, she praised her dancing partner Nikita for “changing people’s lives” and “adapting” their routines, calling him “the best.”
‘What he’s done for my choreography, he realised everyone can dance and has adapted it to me,’ she told former It Takes Two host Rylan Clark.
‘But it shows that choreographers out there can do anything with dwarfism and any different disability.’
Turning to Nikita, she added: ‘You’ve changed people’s lives, he has.’
When presenter Tess Daly asked her about her experience on the show, a teary Ellie said: ‘I’ve literally had the time of my life. It’s been the most incredible experience – life changing really.’
‘I want to thank Nikita ever so much. I’m going to miss him – he’s changed my life and confidence.
‘And all of you guys—the pros. Every single one of you who’ve been part of this Strictly. Behind closed doors, the costume designers, I’ve literally loved waking up every single day and dancing, I’m going to dance forever.
‘It’s incredible, this show is life changing. He’s [Nikita] changed my life. We’ve had the most amazing days.’
Strictly Come Dancing continues tonight at 7pm on BBC One and iPlayer.