LOS ANGELES, Mar. 10 – FBI agents arrested a Manson family girl Saturday to foil what they said was a jail-hatched plot to kidnap a foreign diplomat here.

Maria Theresa Alonzo, 22, still bearing the “X” mark that Manson followers scratched in their foreheads, was arrested at her Hollywood apartment on a federal warrant charging her with violation of federal kidnaping and escape and rescue statutes.

Miss Alonzo was accused of conspiring with two Los Angeles County jail inmates – one of them a convicted skyjacker — to kidnap the counsel general of one of several countries, including Paraguay, Uruguay, Canada, France, Germany, Switzerland or Haiti.

FBI agents think the suspects were most likely to have kidnaped the consul general from Canada, Germany or France, but seven countries were mentioned in an 11-page affidavit filed with the U.S. attorney’s office by William A. Sullivan, assistant FBI director in charge of the Los Angeles office.

The Paraguay and Uruguay consul offices here were closed recently but the alleged conspirators apparently were unaware of that, the FBI said.

The affidavit says the three conspirators were planning to hold the consul for $250,000 ransom, asylum in Sweden and the freedom of the two county jail inmates, Garrett Brock Trapnell and Robert Bernard Hedberg.

Agents said Trapnell and Hedberg planned the kidnapping, then asked Miss Alonzo — Hedberg’s girl friend — to help them execute it.

She then asked a fourth, unnamed person for assistance, agents said, and the fourth person went straight to the FBI.

Miss Alonzo was under surveillance for more than a week. The kidnaping was expected Friday morning, but Miss Alonzo developed a boil, and went instead to County-USC Medical Center for treatment.

On Saturday afternoon, agents decided to wait no longer. They arrested Miss Alonzo, and simultaneously filed charges against Trapnell and Hedberg.

Trapnell 36, was convicted last May of hijacking a Los Angeles-to-New York airliner and demanding a $306,300 ransom, asylum in Europe, the release of a prisoner in a Dallas jail and the release of Angela Davis, then imprisoned on murder charges arising out of the 1970 Marin County courthouse shooting.

An FBI agent posing as a TWA crew member shot Trapnell and thwarted his skyjack attempt.

Authorities described Trapnell as a bizarre character who often carried an attache case, affected a James Bond role, trained two German shepherds to be vicious and boasted that he could beat any criminal charge on an insanity plea.

Trapnell did, in fact, win a bad check case in the San Fernando Valley several years ago with an insanity plea, and when he was arrested after trying to hijack TWA Flight 2 Jan. 29, 1972, he again entered an insanity plea.

His first trial ended in a mistrial, but he was subsequently convicted and sentenced to life imprisonment. He was returned to Los Angeles County Jail recently to stand trial on charges of robbing the Princess Louise restaurant of $10,000 in October, 1971.

Hedberg, 36, was arrested Jan. 29 for unlawful flight to avoid prosecution after a shootout with police in Calexico. He was also charged with assault with a deadly weapon.

Miss Alonzo has been arrested several times, on charges ranging from possession of dangerous drugs to prostitution.

Hedberg, Trapnell and Miss Alonzo will be arrained Monday before a U.S. magistrate In Los Angeles.

By BILL HAZLETT and DAVID SHAW