i'm betting when they met, she was less hot, and he had his stuff together. They got married, he focused on work and got fat. She stayed at home and in a year, got tan & skinny.
he's probably 100% committed, he can get her off, and she trusts him. She's probably been hurt by guys a lot, and wants to feel safe and loved.
and if they're together in 10 years, I'll give her tons of credit. And hey, when they're 60 or 70, they'll both be fat, old, breaking wind in rocking chairs watching cable news or History channel all day, anyway...