The actress, who plays Kat Moon in the BBC One soap, secured the accolade after receiving the most votes from Inside Soap magazine readers, reports the Daily Star Sunday
Wallace won't be at tomorrow's ceremony to collect the award, but her EastEnders co-stars will instead accept it on her behalf.
Should the rumour be true, she will beat Coronation Street's Katherine Kelly (Becky McDonald), Hollyoaks star Claire Cooper (Jacqui McQueen) and Emmerdale's Pauline Quirke (Hazel Rhodes) to the title.
A soap source said: "Kat Moon has only been back in Albert Square a year - but what a year it's been for her. The soap's controversial baby-swap storyline was one of the most talked about ever and once again Jessie pulled off some amazing performances.
"Kat has always been one of the most popular characters in the soap world and since her return she's become even more of an icon. Everyone is excited to see what happens next for Kat and of course husband Alfie."
She recently won 'Best Soap Actress' at the TV Choice awards as well as winning 'Best Actress' at the British Soap Awards in May and All About Soap's Bubble Awards back in March.
Earlier this month, Wallace cancelled her wedding to her husband-to-be Vince Morse after discovering he'd sent an explicit image of her to an ex-girlfriend.
> Inside Soap Awards nominations shortlist revealed