The baptism of the first child of Harry's brother William and his wife Kate is to take place at the Chapel Royal in London's St. James' Palace.
People.com said Harry's romance with Bonas is going well, but they are not established enough as a couple yet to attend such high-profile events together.
"It was always so unlikely that she would be invited. To say she is shy and mulling it over is rubbish," a family friend of Bonas told the magazine.
"If she went to this totally private service, it would be tantamount to saying they were about to be engaged," a second source said.