updated 06/22/2012 AT 1:00 PM ET
•originally published 06/22/2012 AT 4:30 PM ET
A few months after going public with her romance with Jason Segel, Michelle Williams “hasn’t been this happy in forever,” a source tells PEOPLE.
And “Jason is totally smitten,” said the source about the couple, who appeared at an afterparty for the premiere of Take This Waltz at Manhattan’s Sons of Essex restaurant Thursday night. “It’s like the first girl he’s ever been this way with.”
The couple, who only spent about forty minutes at the afterparty, sat down to chat with another couple and mingled with friends briefly before leaving. They appeared in good spirits, laughing together and occasionally holding hands.