The England soccer player grabbed the microphone to do an impromptu version of Bruno Mars` hit `Just the Way You Are` while the pair were partying together in Barnet, London, and Cheryl "loved" hearing him sing the ballad - which includes the line, "When I see your face, there`s not a thing that I would change, because your amazing, just the way you are" - despite his lack of talent.
A source told The Sun newspaper: "Ashley pretty much murdered the song. But Cheryl loved it."
Cheryl, 28, then reciprocated by singing the song `Amazed` by country band Lonestar, which has the lyric, "I`m so in love with you, it just keeps getting better".
The source added: "It was clearly about him."
Despite splitting in 2010 after revelations Ashley had cheated on her with several women, the pair seem to have reconciled in recent months.
At her recent birthday party in June, Ashley was seen dancing with Cheryl and they have also enjoyed a pizza at a get together at the home of her Girls Aloud bandmate Kimberley Walsh.