The couple had been due to fly to America together to attend the wedding of Prince Harry's friend Guy Pelly on Saturday, but Bonas had to pay for her own 650 pounds air fare and did not want to spend so much money if their troubled relationship was doomed, The Telegraph reported.
She chose to grasp the nettle and confront the Prince over their future, which resulted in a "bit of a bust-up" and the decision to go their separate ways, the paper said.
Friends suggested that the pair "might both regret it" and could get back together at a later date.
However, Bonas, 25, was said to have been unhappy for some time, partly because of the strain of being in the public eye and partly because the dance graduate was feeling "frustrated and unfulfilled" at her inability to pursue a career on the stage while dating the Prince.
Prince Harry will now fly to Pelly's wedding without Bonas, accompanied by his brother Prince William, who could use the flight to Memphis to offer some advice after his experience of temporarily ending his relationship with the then Kate Middleton in 2007.
While Prince Harry can look forward to drowning his sorrows, Bonas went straight back to the daily grind yesterday, heading off to work in Soho, the report said.
Bonas, who works in marketing, trudged along the pavement with her hands in her pockets and with her bootlaces undone.
"Cressida was due to go to the wedding but she was paying for her own ticket, and she could only just afford it. She has never complained about paying her own way, though she has been hard pushed to do so," a friend was quoted as saying.
"The widespread opinion that she is a wealthy heiress is complete rubbish, so it was quite a stretch to go to Guy Pelly's wedding. Guy is not a close friend of hers so there would have been no point in going if she and Harry were splitting up," the friend said.
Bonas, who earns around 20,000 pounds and prefers not to rely on financial support from her parents, does not have the sort of money at her disposal to keep up with her boyfriend, the report said.
Friends made clear that while the timing of the row may have been prompted by the imminent trip to the US, the row itself was not about the air fare, but was about the couple's long-term future and Bonas's increasing unhappiness.