The 50-year-old, who plays Eve Unwin on the BBC One soap, was diagnosed with breast cancer in October last year.
But despite her health issues, she bravely continued to film for the soap.
The soap star went on to have chemotherapy as well as undergoing a left breast mastectomy and a reconstruction.
Heather took to Instagram on Thursday to update her fans on her journey, writing: “Final round of 15 radio therapy sessions just completed.
“This marked the end of long 9 months of diagnosis, surgery, chemo and radio.
“Time to piece myself back together. Thanks for all the beautiful support. #checkyourbreasts #breastcancerawareness”.
Fans flooded with comments of admiration and support, with one writing: “What an amazing woman. Her sheer will and determination to keep filming whilst battling this awful disease has been unbelievable.”
Another added: “What a legend, wishing her all the best in her recovery.”
A third penned: “As someone going through a similar diagnosis, seeing Heather on the other side of treatment is incredibly inspiring.”
Just as she was about to begin radiotherapy, Heather revealed the heartbreaking news last week that her wife Ellie has also been diagnosed with the disease.
She told the Mirror: “Her breast cancer was a smaller, aggressive lump, so she had a lumpectomy and then radiotherapy.
“Of course, then I come along with my 12cm lump, absolutely ginormous, and mastectomy, chemotherapy, just about to go into radiotherapy.
“She’s like ‘Even that you have to do bigger.’ It’s like ‘Hold my beer.'”
This comes after the star revealed decided to continue filming for her dramatic wedding scenes just hours after her cancer diagnosis.
Her character was embroiled in dramatic scenes, which included her wedding to Suki Panesar as well as being poisoned by Suki’s ex-husband Nish Panesar.
Revealing why she decided to continue working, she told Gaby Roslin on her podcast that she wanted to film the important scenes because she feared she would die.
The former Waterloo Road star expressed: “We got back to Brighton at 7 o’clock, and I was on the road at 10 past five that morning, to Elstree, to start possibly the two biggest weeks that I’ve done on EastEnders.”
Heather explained that she had told bosses about her diagnosis and was told she didn’t need to come in while she was taking in the life-changing news as well as undergoing treatment.
“I said ‘I need to come in’ because at this point I don’t know what’s going to happen,” she continued.
“And I want to finish this arc of the story. Not coming in for the next two weeks is not going to change anything, but at least let me put the full stop on a story that’s been playing out for nearly two and a half years.
“If we get to the end of that and we see them get married and we see them successful, if beyond that it’s a mess, I can leave and feel like I’ve put a full stop on something.”
