DALLAS — A woman who wanted to visit her dying mother one last time was removed from a plane and left in tears after an online travel agency canceled her ticket just before the flight.

The travel agency blames it on a mix-up that started when the woman changed flights without telling them. The agency says it was trying to protect her from fraud.

Carrol Amrich of Pueblo, Colo., said Friday that United Airlines offered no empathy or help for a clearly distraught traveler.

After Amrich learned that her mother, Dixie Hanson, was hospitalized in Minnesota on Jan, 16, her landlord went on Traveler HelpDesk and bought a $585 United ticket.

Hanson’s condition worsened, however — she was not expected to live through the night. The landlord, Ines Prelas, called United and paid $75 more so Amrich could fly standby on an earlier flight, and the two rushed to the airport in Colorado Springs. She would fly through Denver to Minneapolis.

Amrich said everything seemed fine as she gave her boarding pass to a United agent, stowed her bag and took a seat on the plane. But a minute or two later, the agent came on board to tell Amrich that her ticket was no good; it had been canceled.

“I said ‘I’m trying to get home to see my mother. She’s dying,”’ Amrich said. “She goes, ‘I can’t help it. You have to have a ticket, no one flies for free. Please disembark.’ I knew at that time I’d never see my mother again.”

Traveler HelpDesk had canceled the ticket. Carolyn Gallant, a customer-service supervisor, said the online travel agency voided the ticket because it didn’t know that Amrich’s landlord had changed the flight by calling United directly.

Gallant said the agency only knew that Amrich was no longer booked on the original flight, and it was trying to protect her from possible fraud. She said the mix-up would have been avoided if the customer had called the agency instead of United.

Back at the airport, Amrich and Prelas were pleading with United to let them buy a new ticket to get back on the plane — it was the last flight of the night. Amrich said the United agent told them there wasn’t time for that, and that they would reopen the next morning.

Amrich wound up driving to Minnesota. A couple hours into the trip, she got word her mother had died.

In a statement, United Airlines referred questions about the ticketing mix-up to Traveler HelpDesk. It said Amrich couldn’t buy a new ticket at the airport gate in Colorado Springs because the plane had already left — Amrich disputes that.

United said it refunded all money spent on the ticket and fees, and it offered condolences to Amrich and her family.

Amrich’s landlord posted an account of the events online, and it was first reported by The New York Times.