The actress is said to be blissfully content with the How I Met Your Mother actor.
Engagement rumours have surrounded the couple, who went public with their romance in April.
Not only is Jason devoted to Michelle, he is committed to being a good 'stepdad' to Matilda, Michelle's six-year-old daughter with late actor Heath Ledger.
Jason has reportedly even reached out to Heath's family to let them know he has the little girl's best interests at heart.
The 32-year-old star apparently told Health's parents they are welcome to spend as much time with Matilda as they like.
He spoke to Heath's father Kim, telling her the family could stay in his home whenever they flew in from Australia to visit.
"Kim was blown away by Jason's generosity and the two hit it off right away," a source close to the Ledgers told Radar Online.
"Now Kim's given his blessing for Jason to marry Michelle and be a stepdad to Matilda."
Heath and Michelle split in 2007 after dating for three years and welcoming their daughter in October 2005.
Heath died in January 2008 after overdosing on prescription drugs.