The 39-year-old actress and the 42-year-old actor - who made their red carpet debut as a couple at the Golden Globes in January - recently called time on their romance, according to PEOPLE.
A source told E! News: ''She's absolutely devastated.''
Rachel - who has five-year-old daughter Briar Rose with ex-partner, 'Star Wars' actor Hayden Christensen - first sparked speculation she was dating her 'The To Do List' co-star when they were seen holding hands as they went out for coffee with members of Bill's family in his hometown of Tulsa, in Oklahoma, in December.
She was also seen having dinner with the actor - who has daughters Hannah, 10, Harper, seven, and Hayley, five, with ex-wife Maggie Carey - at a Los Angeles restaurant in November but they did not go public with their romance until January 2020.
And the pair enjoyed a romantic getaway to Orange County, California, together in February.
A source said at the time: ''They spent Valentine's weekend in Orange County, California. It was a quick getaway, but time for the two of them to be together without any distractions.
''Rachel is very happy dating Bill and is excited about being with him. He treats her very well and is hilarious and fun.''
Meanwhile, Rachel previously admitted she would never date anyone who isn't fully invested in supporting her as a mother.
She recently said: ''I was talking to these guys a few months back, anytime I would bring my daughter up, they would never pursue the question or ask more about her.
''It was a red flag because anyone that you're going to get involved with, if you have a kid, they have to be all about the kid.''
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