Halliwell, 41, started dating Horner around January earlier this year, and it is said that the Formula One boss proposed to her a few weeks ago, reported Daily Mirror.
"Geri is delighted and has been telling close friends about the plans - but they have been more cautious around his family. They made the decision to get engaged this spring but have kept it quiet to avoid any awkward fall outs.
"Some of his family are still unsure about the situation. They weren't impressed at the breakdown of his relationship with Beverley just six months after the baby's birth," a source said.