MANAGUA, Nicaragua (AP) _ A former rebel leader returned Friday night after more than two years of exile, saying she will fight the Sandinistas in the political arena instead of with weapons.

Azucena Ferrey, a former member of the Nicaraguan Resistance directorate, flew in from Costa Rica and was greeted by about 40 cheering supporters, most of them from the Democratic Christian Party.

''At this time the battlefield is on the political field,'' Ms. Ferrey said when asked if her return meant she cut herself off from the rebels, known as Contras.

She had to sign a document upon arrival stating she did not support armed struggle against Nicaragua, something required of all returning exiles but something no former member of the Nicaraguan Resistance had ever done.

''I have been forced to fulfill a requirement in order to be allowed back into my own country,'' Ms. Ferrey said. ''But the struggle of the Nicaraguan people is well worth bending one's pride.''

Asked if her return signaled the end of armed struggle, Ms.Ferrey said: ''Why don't you ask the Sandinista Front?''

The U.S.-backed rebels have fought the leftist Sandinista government since 1981. In August 1987, the five Central American presidents signed a peace plan whose provisions include an end to insurgencies and to outside aid to rebel groups.

Adan Fletes of the Social Christian Party was at the airport to greet Ms. Ferrey and said she would run for a National Assembly seat in general elections scheduled for Feb. 25, 1990.

Fletes said Ms. Ferrey came here at the invitation of the January 22nd Movement, a group of mothers and relatives of political prisoners. The name comes from a Jan. 22, 1967 opposition march which ended in a bloody confrontation with soldiers of dictator Anastasio Somoza, who later was ousted.

Fletes said she will join a march organized by 15 political parties and opposition labor groups set for Sunday in Masaya, 20 miles east of Managua.

Ms. Ferrey said she planned to stay about a week but intended to return to Nicaragua permanently.

A hardliner on the Nicaraguan Resistance directorate, she resigned last fall after an internal quarrel in which former National Guard Col. Enrique Bermudez, Contra military leader, also became the political leader.

Ms. Ferrey's brother, Roberto Ferrey, is on the directorate now.

Also Friday, wildcat strikes by teachers seeking higher pay waned after the government expelled two U.S. diplomats, accusing them and right-wing parties of instigating the walkouts.

Negotiations were reported in eight cities among teachers, government representatives and the pro-Sandinista national labor union from which some educators have defected.

But teachers at San Rafael del Sur, 30 miles south of Managua, remained on strike Friday, and a partial strike was reported continuing in Chinandega, 80 miles northwest of the capital

The government said Thursday it was expelling two U.S. diplomats who it said attended teacher meetings in Chinandega the day before and promised money to encourage strikes. The U.S. Embassy denied the charges.