Michelle Williams' daughter is pressuring her to marry Jason Segel.

The 'My Week with Marilyn actress has been dating the 'How I Met Your Mother' star for around six months and six-year-old Matilda - her little girl with the late Heath Ledger - is keen for him to become a permanent fixture in their family life.

A source said: ''You should hear Matilda talk - she wants to be a flower girl, and she tells her mom she wants a little sister. She knows that won't happen if Momma doesn't marry Jason - so she's pushing for it.''

Insiders say Michelle - who was not with Heath at the time of his death from accidental DRUGS overdose in January 2008 - is smitten with Jason and they wouldn't be surprised if they listened to Matilda's pleas and tied the knot before the end of the year.

One added to Enquirer magazine: ''Jason lives to make Michelle laugh, and that's pretty hard for a girl to resist. Plus, he's shown he'd make a great daddy. Bet on a marriage by the end of the year.''