The US actress, who will tie the knot with Prince Harry in May, puts herself through twice-daily weight sessions designed by the tennis champ.
Serena, who is famed for her physique and fitness, is set to be a bridesmaid at the Windsor wedding.
A friend of Meghan, 36, said: “Serena has got Meghan doing these tough weights sessions that will have her in incredible shape for her big day.
“Meghan told Serena she wants to have a strong but sexy physique when she walks down the aisle. She doesn’t want to be super-skinny.
“So Serena drew…