TAMPA, Fla. (AP) — If you were to diagram the increasingly tangled sex scandal surrounding former CIA Director David Petraeus, nearly all lines would lead back to one person: Jill Kelley, a 37-year-old Tampa socialite who hosted parties for the nation's top military brass.

The raven-haired woman's complaint about anonymous, threatening email triggered the investigation that led to Petraeus' downfall. And now she is at the center of an investigation of the top U.S. commander in Afghanistan over alleged "inappropriate communications" between the two.

Kelley is a close friend of the Petraeus family, and photographs circulating the Internet show her posing for pictures at parties, sometimes in short dresses with Petreaus, his wife, and sometimes her husband, a cancer surgeon. Kelley served as a sort of unofficial social ambassador for U.S. Central Command in Tampa, hosting parties for the general when he was commander there from 2008-10.

She met Gen. John Allen while he was at Central Command, and now investigators are looking at some of the 20,000-plus pages of documents and emails between Allen and Kelley that have been described as "flirtatious," according to a senior defense official who spoke on condition of anonymity because he wasn't authorized to discuss the case publicly.

Allen denies that he has engaged in any wrongdoing.

For her part, Kelley has kept a low profile since Petraeus' affair with his biographer, Paula Broadwell, became public after Kelley told an FBI agent that she had received a threatening email, which later turned out to be from Broadwell.

Investigators are still looking into whether any classified documents were ever leaked or in the wrong hands.

Outside Kelley's stately, two-story brick home in South Tampa, a horde of media gathered. A woman believed to be Kelley was seen inside the large windows of the house, which has a half-dozen white columns, black shutters and a neatly manicured lawn. A silver Mercedes S500 in the driveway has a license plate marked "Honorary Counsel," perhaps belonging to Kelley's twin sister, Natalie Khawam, who is an attorney also lives at the home.

Ken Walters, a neighbor, called the Kelleys good friends, but said he doesn't see them all that often. Walters said he went to a party the couple had to celebrate their first son's baptism. The Kelleys have two other children.

"Natalie and her sister, they're certainly not shrinking violets," he said.

Jill Kelley's brother David Khawam told WPVI-TV in Philadelphia on Monday night that details of the allegations surged fast.

"It's happened extremely quickly, we're talking 12, 24 hours, maximum, since we've found out about this. It's a shock. We're trying to figure out where the pieces are falling right now," Khawam said in the interview done at his offices in Westmont, N.J.

He said that his family left Lebanon for Huntingdon Valley in Montgomery County in Pennsylvania in the 1970s to escape turmoil and fighting. His parents opened a Middle Eastern food restaurant in Vorhees, N.J., called Sahara. Continued...