Danielle Harold was reportedly in tears after recently being told her character Lola Pearce would be killed off the show - but Cassidy, who has played Sonia Fowler since 1993, said it was the nature of being in soap.
Talking to Metro at Saturday's British Soap Awards, she said: "It’s soap. It’s what happens. To get good stories, you need people to exit and you need people to come in. It’s just the way of the show.
"Exits and entrance is a part of soaps. So it just is what it is."
As well as Harold's Lola, characters Stuart Highway (Ricky Champ), Dana Monroe (Barbara Smith), Peter Beale (Dayle Hudson) and Jada Lennox (Kelsey Calladine-Smith) are also being written out.
However Cassidy, 39, who has starred in the BBC One soap off and on since she was 10, sounds as though she would be less relaxed about her own Albert Square alter ego being killed off.
She said that Sonia was "part of the fabric of the show" and that she hopes "she will always stick around".
Cassidy also praised new EastEnders boss Chris Clenshaw, saying that his joining the show, a newly-built set and the introduction of fresh characters had made for an exciting time in Walford.
She said: "I just always want someone who loves the show as much as I do. It’s just lovely to be in a place where we’re starting afresh."
EastEnders picked up some big awards at Saturday's ceremony, including Outstanding Achievement for Letitia Dean who plays Sharon Watts, Best Comedy Performer for Tameka Empson as Kim Fox, Best Newcomer for Ross Boatman as Harvey Monroe, and Best On-Screen Partnership for Lacey Turner and Gillian Wright as Stacey and Jean Slater.
But it was Emmerdale that bagged the biggest wins for Best Soap, Best Leading Performance (Paige Sandhu), Best Dramatic Performance (Mark Charnock) and Best Family (The Dingles).
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