The Piranha 3D star called time on her two-year relationship with Evans last week and he has reportedly moved out of their shared home in London.
The news comes amid reports Brook has been regularly meeting up with another rugby ace - her ex-lover Danny Cipriani.
A source tells The Sun newspaper: "She's never stopped loving Danny. Even though there was nothing going on while she and Thom were together, Thom hated the fact she was seeing him and Kelly refused to end their meetings.
"After one row too many the pair decided to end things. She's been leaning on Danny since the break-up and, while she's devastated, she knows it's for the best."
Brook, who has previously been linked to actors Jason Statham, Billy Zane and Matthew Morrison, began dating Evans in 2010 shortly after she separated from Cipriani.
In May 2011, Kelly miscarried the couple's baby daughter.