The TV star, known for roles in Coronation Street and Waterloo Road, will be playing Trish, mother of Maxine Minniver – played by Sanderson – a dance teacher “with a dark side”.
Welch previously starred opposite Sanderson in Coronation Street, when they played Natalie Barnes and Candice Stowe respectively.
She told ITV show Loose Women, where she is a panellist: “I’m going to be playing my lovely Nikki Sanderson’s mum, Trish, who is a dance teacher with a slightly dark side.”
Welch, who has been married to artist Lincoln Townley since 2013, joked her husband might need to step in as a body double for some scenes.
“I’ve got a hunky new lover,” she said.
“Because of Covid restrictions, he’s probably very glad he doesn’t have to kiss me, but they’ve also mentioned there may be times that Lincoln might have to be a body double if there’s any jiggy jigs.”