The woman said a boy stole her purse and ran from the train after it stopped. A mix of boys and girls repeatedly punched her, and some girls hit her with purses. She said she also was hit with a can of beer.
She said the attack escalated when the group turned on her while harassing another, older woman, who had asked the teens to tone down their act. There was no transit security on the train, she said.
"I did not intervene," the Vancouver woman said, adding that she had tried to ignore them. "They got in my face.
"Finally, I just said, 'I don't care what color you are, if I want you out of my face, I'd tell you to get out of my face.' "
That's when the teens got physical. She said she tried to fight back but was punched and stepped on.
"Then they took my purse, and then they ran out" of the train, she said. "And then I was standing at the door, on the phone with 9-1-1 because nobody would call."
The four teens are accused of robbery, assault and intimidation. The intimidation count stems from the alleged racial comments, said Sgt. Brian Schmautz, a police spokesman.
Fetsch, the TriMet spokeswoman, said the train operator alerted transit dispatchers that there was a fight on board the train and to call police.
Aimee Green, Wade Nkrumah and Joseph Rose of The Oregonian staff contributed to this report.