"She's doing well. She's absolutely fine," the friend, who answered Foster's cell phone on Sunday, told the New York Post. She said Foster, a 36-year-old divorced mother of three, has been communicating with Usher, 28, since Saturday. They are expecting a child together in the fall.
"They are still best friends. Why would anyone assume otherwise? People have assumed so much that was wrong about the relationship."
On Sunday, crews drove up the winding driveway of music mogul L.A. Reid's 10,000-square-foot mansion in New York's Sagaponack, Long Island, ready to break down preparations for the lavish wedding, the Post reported.
It is believed the 70 to 100 guests, including Janet Jackson, Jermaine Dupri, Beyoncé and Jay-Z, were told just hours before the big event not to bother showing up, the Post said.
Although no official explanation was given, it is believed Usher's mother and former manager, Jonnetta Patton, did not approve of Foster, and had not been invited to the wedding.
On Sunday, Usher was bound for Atlanta to make peace with his mother, sources told the Daily News.
"The reason he called off the ceremony is that he couldn't go through with it without Jonnetta," said one insider. "He had an eleventh-hour epiphany."
The Grammy-award winning artist also reportedly had a falling out with his godfather, actor Ben Vereen, over the relationship and had cut him from the guest list.
Denying rumors that his fiancée was a control freak, Usher recently said in an open letter to People magazine: "I am happy, excited, completely clear and independent on my direction, feelings, decisions and I am NOT BEING LED," he wrote.
A National Enquirer story, leaked just days before the planned nuptials and due to be published this week, quoted Foster's half-sister saying the bride-to-be was an ex-con who had done time for petty theft.
Usher began dating his former stylist about 18 months ago, and they got engaged in February. In June, Usher announced that he and Foster were expecting their first child together.
"We are extremely excited at this point in our lives planning our wedding and the joy that comes with expecting our first child together," the couple said in a statement released to The Associated Press. "We hope people will be happy for us and respect our privacy during this happy period in our lives."
Foster was recently divorced at the time of the announcement.
Usher is soon expected to release the follow-up to his eight-million selling, Grammy-winning album "Confessions," released in 2005. He also has a fragrance due out in September.
The Associated Press and the New York Post contributed to this report.