Mary-Louise Parker is engaged.

The actress was thrilled when her 'Weeds' co-star Jeffrey Dean Morgan popped the question earlier this month. She has excitedly told friends of her plans to wed but hasn't set a date for the forthcoming ceremony.

A source close to the couple said: "They're thrilled as they're really happy together. They can't wait to exchange vows and become man and wife."

Mary-Louise and Jeffrey - who plays Mary-Louise's character Nancy's dead husband in the hit TV show - began dating in 2006 but briefly split in June 2007.

They soon rekindled their romance and, last December, Mary-Louise, 41, accompanied Jeffrey, 43, to the U.S. premiere of his movie 'P.S. I Love You'. Last November, Mary-Louise adopted a baby girl from Africa.

A source said: "Mary-Louise is such an incredible mom. She couldn't be happier about this."

The actress also has a three-year-old son, Will, from her relationship with actor Billy Crudup.