The 41-year-old actress, who played Mel Owen between 1998 and 2002, was heavily involved in some of the BBC soap's biggest storylines of the era.
She told PA: "I don't think you're ever really prepared. I do remember when I was told I had the job, the executive producer, Matthew Robinson, said to me, 'Be prepared for your life to change', but I don't think I realised just how much it would change.
"Because I was a jobbing actress before, and I was only doing a three-month contract, I never really saw the big picture and just thought, 'Oh, this is a nice job'.
"And then it turned into a three-and-half-year nice job! Also, I was 28 - if it had happened to me as a teenager, it would have been a different thing."
The star is married to fellow former Albert Square cast member Tom Ellis, who played Dr Oliver Cousins in 2006.
While Outhwaite remains open to an EastEnders reappearance, she has acknowledged that a return storyline may prove difficult to write.
Watch a classic Mel moment in the video below: