The Girls Aloudbabe is so scared that she has warned the Chelsea star: "Keep away from that woman."
The singer is so disgusted by stories claiming Vanessa Perroncel slept with a string of Blues players that she now wants nothing to do with her.
Cheryl and Ashley were such best pals with Vanessa that while she was dating Premier League ace Wayne Bridge the couples holidayed together in the south of France.
But that all changed after French beauty's fling with Blues skipper John Terry and rumours of affairs with other Chelsea stars.
There is no suggestion 29-year-old Ashley has cheated with Vanessa, and the lingerie model has denied the allegations of flings with Blues stars.
But friends said Cheryl is determined to distance Vanessa from her fella - especially with stories of Ashley's own alleged cheating "very fresh" in her mind.
A pal of the sexy X Factor judge revealed: "All the WAGs fear Vanessa might have made a play for their husband in the past.
"It would be understandable if Cheryl felt the same."
Vanessa split with Bridge, father of her son Jaydon, last July, three months before she was linked with Terry, 29.
But her fling with the Chelsea skipper prompted Cheryl to write to Bridge to offer her support to him and three-year-old Jaydon.
Ashley hit the headlines in 2007 after claims he bedded 22-year-old hairdresser Aimee Walton during a drunken one-night stand.
The pal added: "This situation has opened up old wounds for Cheryl. She's forgiven Ashley but wants to keep him out of trouble.
"He's friends with Terry and she doesn't want him in a crowd of lads drinking and chatting up girls.
"She'd probably like it if he quit Chelsea."
Terry, 29, who has since been linked with a host of other women, is said to have got Vanessa pregnant and paid for an abortion during the four-month fling.
When the news broke, his wife Toni, 26, fled to Dubai with their three-year-old twins Georgie and Summer. Terry is rumoured to be joining her at the weekend for an emotional Valentine's Day reunion.
