Show bosses broke the news to the actress late last year, but in a coincidence, it was on the same day that she was celebrating after hearing that her Moroccan husband Yassine Al-Jermoni had been granted a visa to live in Britain.
Fergison, speaking in a new interview with Best magazine, explained: "It was a bittersweet day. What you get with one hand, you get taken away with another!
"When they told me Heather was for the chop, [they] had to get me a tissue. Sometimes a character is sacrificed to make other stories work. I get it. I knew it was going to come, but it was still a shock."
The 48-year-old added that her most emotional moment came when she cleared out her dressing room after filming her final scenes earlier this year.
"There were lots of tears and I was scared about the future," she confessed. "I've turned down a couple of things I didn't think were quite right for me. I'd love to do some documentaries about Morocco with my husband and I'd like to do some more theatre."
EastEnders fans saw Heather's final episode last night (March 19) as she was killed by twisted teen Ben Mitchell.
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Watch Heather's EastEnders character trail below: