From Fictiondb:
She didn't intend to deceive him

When Philomena Peabody met her boss's son, he was suffering temporary snow blindness. "You sound like somebody's mother;" Penn Wilderman said, convinced by her no-nonsense attitude that she was "a sweet little old lady."

Even after she'd moved into his luxurious mansion to help look after his son, Phil couldn't disillusion Penn about her age.

To help win a custody battle for his teenage son, Phil agreed to marry Penn. But she dreaded facing him once the bandages were off, and he could see his attractive twenty-seven-year-old wife....