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....