Viewers will see her receiving treatment and declaring: “One thing you must do is not give up, you must remain positive. Don’t give up — it’s not the British way of doing things.”
She added: “I want to show people that chemotherapy is not a death sentence — it is medicine and it saves lives.
“You must never give in — you have to fight. I’m not going to feel sorry for myself, there are thousands of people across the country going through what I am."
Richard, who featured in the long-running BBC soap as Pauline Fowler for 21 years, had fought to overcome cancer twice previously, first in 1996 and again in 2002.
After lengthy treatment her cancer went into remission but last year an aggressive form of the disease returned and in October she revealed her condition was terminal.
She died last month at the Harley Street Clinic in London with her Ulster-born husband, John Burns, by her side.
The documentary, to be shown on BBC1 at 8pm tonight, shows her joined by former EastEnders co-stars James Alexandrou and Natalie Cassidy on the night before she picked up scan results in December.
Speaking of his wife’s death, Mr Burns (45) said: “Wendy and I were looking forward to a holiday and just a few hours before she passed away she was sitting up chatting.
“I went to walk Lily our dog and when I came back they asked me to come quick and said I had to say my goodbyes. She passed away peacefully as I held her hand.”
Wendy Richard: To Tell You The Truth is on BBC1 tonight at 8pm
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