A 9-year-old girl from Fort Worth, Tex., showed up in Washington Tuesday with an unusual request. She wanted to see Jimmy Carter to ask him to issue a presidential pardon to her mother, who is serving a three-year prison sentence at a minimum security federal institution in Fort Worth.

The girl's name is Sandra Chandler, and while much remains unclear about her adventure, this much seemed clear: She delved into her piggy-bank, according to her sister, went to a travel agency, where she purchased a S114 one-way ticket to Washington and had about $20 left over, boarded a Braniff Airlines plane by herself at the Dallas-Fort Worth Airport, got off in Washington and told Braniff officials she wanted to see the President.

She failed in her attempt to see Carter. But she spent two days in Washington, got inside the White House, met with presidential assistant Margaret (Midge) Costonza and other officials, including a Justice Department lawyer, and bumped into Jody Powell in a White House hallway.

"She got to talk to everybody but the one who could help her," Sandra's sister, Pepper Summers, said in a telephone interview last night from her home in Houston.

The girl's story became known yesterday because Pepper Summers and another sister, Delilah Chandler, who lives with Sandra in Fort Worth, were angered that she had failed to see the President and began calling newspapers and television stations to complain.

"How can you tell a 9-year-old girl she has to have an appointment to see the President?" Pepper Summers asked, indignantly claiming that is just what a White House secretary had told the girl.

Costanza, who heads the White House office of public liaison, said she first heard of the girl when Braniff officials called her at the White House and told her of Sandra's request to see the President. She was taken to the White House for a meeting with Costanza. In the meantime, her sister Delilah was called in Forth Worth, and she flew to Washington later Tuesday.

The two sisters stayed overnight in Washington - where exactly is not clear - and met Wednesday at the White House with members of Costanza's staff and a Justice Department lawyer. Turned down on the pardon request, they returned to Fort Worth Wednesday night.

The background on the mother's case remained murky last night. According to Pepper Summers, the mother was jailed last February for jumping bail in connection with anther case.

Costanza said she sympathized with the girl and was moved by her attempt to help her mother. She said Sandra offered little in explanation about how she managed to get to Washington or what inspired her to make the attempt.

"She said she knew the President was the only one who could give pardons," Costanza said.

According to Pepper Summers, the first word of Sandra's adventure came in a note to her sister Delilah found in the bathroom of their Fort Worth home Tuesday morning. The note said she had gone off "to do something to help Mom" and not to worry.