Apart from a the occasional post-rehearsal dinner in NYC , Katie Holmes , 29, has isolated herself since she moved to the city in July.

Katie Holmes isolates herself from friends?

She's ignored old pals such as her Dawson’s Creek co-star Michelle Williams, 28, who lives nearby with her daughter, Matilda, 2, OK reports.

And it's been months since Katie was spotted with any of her old celeb pals like Kate Beckinsale, Eva Longoria Parker or Victoria Beckham.

“Katie and I were best friends until she met Tom,” the source tells OK!. “Then, overnight, we went from talking every day to nothing. She was so single-minded about her life with him that no one else mattered.”

Another source agrees, “Katie never had a big group of girlfriends, but after Tom, she stopped calling them.

"It was amazing she could cut everyone off so fast — business associates, her hair and makeup team, as well as friends.”

However, an insider explains, “Katie is taking this Broadway role very, very seriously.

"Maybe even a little too seriously. Katie has always been focused and knows exactly what she wants.”

Image WENN