Lisa, 41, was pictured at LAX Airport looking very glamorous as she showed off her new blonde locks.
The make-up artist sauntered through the terminal wearing a navy blazer over a black top.
Lisa gave onlookers a glimpse of her lean pins as she teamed her outfit with a pair of tiny denim shorts.
Ant’s estranged wife completed her airport attire by wearing oversized sunglasses and swept her newly-dyed locks into a low ponytail.
The beauty also flashed her wedding ring as she made her way outside.
Lisa’s trip to America comes after she took to Twitter to comment on the allegations that Ant is dating their former personal assistant, Anne-Marie Corbett.
Last weekend, The Sun reported Ant, 42, has found love with separated mother-of-two Anne-Marie, also 42, in the months following his split from Lisa.
After the news broke, Lisa took to Twitter to share two broken heart emojis followed by a full heart with her 116,000 followers.
She also responded to messages from fans who had commented on Ant’s new reported romance.
One of her followers wrote: “So much for the girl code. Keep that gorgeous dignified chin held high. Wishing you nothing but happiness in the future.”
“Exactly!” Lisa replied, retweeting the message.
She also replied to a second which read: “Sending my love Lisa!! Really feel for you worst pain ever.”
“Thanks babe and to think she was MY friend!” Lisa blasted.
She also said she had found out about the rumours from the press.
Replying to one Twitter user who said they “hoped he didn’t let her find out from the media”, Lisa wrote: “Nope. Just how you guys did,” followed by a broken heart emoji.
Yesterday, it was reported Lisa was no longer in contact with Declan Donnelly and his wife Ali Astall following the breakdown of her marriage to the Ant and Dec star earlier this year.
Lisa is said to be feeling “isolated” from their friendship circle, following the news Ant has allegedly moved on.
A source told the publication: “After knowing each other for so long Lisa felt that everyone had become friends in their own right – but obviously after what has gone on the divided loyalties have become obvious.
They added: “It’s yet another complication in a situation which has got extremely messy.”
Express.co.uk has contacted a representative for Lisa and Dec for comment at the time.
A representative for Dec declined to comment.
Ant confirmed his split from Lisa in January, with a representative saying: “In response to the recent speculation in the media, Ant is very sad to announce that, after 11 years, he is ending his marriage to Lisa McPartlin.
“Ant asks for privacy at this difficult time, for both himself, Lisa and their immediate families,” the statement continued. “No further statement will be made.”