Britney Spears like a “cash cow” as she waded into the row over whether the pop star is being controlled.Cher is the biggest name yet to get behind the movement to “free Britney”, which was started by fans who want to see her win back control of her finances, career and children.The Believe singer tweeted: “She worked hard, was the golden goose, made lots of $$, got sick, now she’s the cash cow.”Cher’s endorsement has added more momentum to the campaign, which has its own hashtag,