Roxy has developed strong feelings for Alfie (Shane Richie) in recent weeks as they have been working closely together at the Queen Vic.
Next week's episodes see Roxy tell Alfie that she's in love with him, leaving viewers to wonder whether the pub boss will stay faithful to wife Kat.
Simons told All About Soap of the aftermath: "Roxy knows it can't happen, but she can't help being in love with him. She leaves The Vic and says she just can't work there any longer. She just decides she has to leave because he goes on and on about Kat. It's too much for her."
Asked whether she wants Alfie and Roxy to have a full-blown affair, the actress replied: "At this point, no, I don't. It's much nicer as a slow-burning thing - you get to play stuff with more depth as you've had time to live with it. Then the audience will hopefully invest a bit more into each part of the storyline."
Simons predicted that there would be fireworks in Walford if Kat learned of Roxy's feelings. The feisty landlady is currently away looking after her father Charlie, who suffered a stroke.
"I imagine it would be the cat fight of the year on Albert Square," Simons said. "I am sure it will happen eventually, but I really don't know when that will be. So just watch this space."
> EastEnders' Shane Richie: 'I hope Alfie doesn't cheat on Kat'
> EastEnders' Alfie Moon to hear Roxy Mitchell's feelings
> Read more EastEnders spoilers and news