Sophie Cruz, the pigtailed girl who darted past security last fall to deliver a letter to Pope Francis, returns to Washington on Thursday as an invited guest of President Obama.

Her presence at a Rose Garden event for Cinco de Mayo will draw new attention to the challenges facing undocumented immigrants in this country.

While the six-year-old was born in California and is an American citizen, her parents crossed the border from Mexico illegally and cannot pass the background checks that would be required to accompany her into the White House.

The emailed invitation requested a Social Security number, which Zoyla and Raul Cruz do not have.

Sophie instead will be accompanied by filmmaker Paola Mendoza, who recently created "Free like the Birds," a mini-documentary on the Cruz family that premiered at the Tribeca Film Festival in New York last month. The advocacy group FWD.us worked with the White House to facilitate the visit.

Zoyla Cruz said it will be "difficult" for her and her husband to wait outside while their precocious daughter attends the celebration and, possibly, meets the president. "But we will . . . enjoy the fact the she is fulfilling her goals."

Last September, cameras from around the world captured security officers hoisting Sophie, then age 5, up to Pope Francis as his motorcade paused near the Ellipse in downtown Washington. Her small arms reached across his white robe so she could give him a hug, kiss, letter and T-shirt.

In the letter, Sophie asked the pontiff to talk to Obama and Congress about the more than 11 million undocumented immigrants living in the United States. The little girl's fear that her parents could be deported motivated her to speak out, Raul Cruz said. "She understands the reality of what could happen to us."

The Cruzes crossed the border a decade ago from southern Mexican state of Oaxaca in search of economic opportunity. Raul Cruz works in a factory, and Zoyla Cruz manned a retail cashier before becoming a stay-at-home mom.

Sophie was a spark from birth, her parents say, quickly learning the songs Zoyla sang to her in Spanish and, starting at age 3, performing folk dances in front of large crowds for local Oaxacan organizations. She recites poetry, skipped kindergarten and reads at two levels above her grade, often teaching her parents, who speak little English, what she has learned.

"She was telling me the other day that she was so surprised to learn that Lincoln did not die [naturally] but was killed when he went to the theater," Zoyla Cruz said in Spanish. "She explains these things to me."

When Sophie starting asking to visit her grandfather in Mexico, it was her parents' turn to explain - that they could not bring her across the border, because they were in the United States illegally, and would not be able to easily come back.

The Cruzes said their daughter wanted to find a solution. When there wasn't a clear one, the girl suggested they fight.

"She is incredible," Raul Cruz said. "She leaves us speechless sometimes."

By last year, Sophie's dancing and eloquence had drawn the attention of the advocacy group La Hermandad Mexicana Transnacional. As the U.S.-born daughter of undocumented parents, group leaders thought she would be an effective - and adorable - advocate for Obama's proposals to shield from deportation illegal immigrants whose children are U.S. citizens.

The organization brought Sophie to Washington for the pope's visit. Her dad came along, paying his own way.

La Hermandad Mexicana Transnacional had talked about finding a way to grab the pope's attention as was done in Rome with another girl, Jersey Vargas. But Sophie's dash past the barriers was spontaneous, said Gloria Saucedo, a well-known Los Angeles activist and director of the group.

"We cannot force a child to do anything," Saucedo said. "Kids like Sophie grow up faster than others because they learn to defend their parents."

Raul Cruz said he started to lift Sophie over the security barrier, but hesitated over whether to set her down on the other side. She then wriggled out of his arms and made a beeline for the popemobile, launching herself and her family into an international spotlight.

Two weeks ago, Sophie sat in the Supreme Court hearing room with her mother for arguments in U.S. vs. Texas, a case that will determine the constitutionality of two executive actions by Obama that aim to shield up to 5 million undocumented immigrants from deportation. Zoyla and Raul Cruz would likely be eligible for temporary relief through DAPA, or Deferred Action for Parents of Americans, because of Sophie and her two-year-old sister Sahara.

The encounter with the pope that made her famous also sparked some criticism from people who said Sophie had been coached and was being exploited by activists. But Sophie's defenders, including her parents, say she has always had a mind of her own and much of the what happened was of her own making.

After presenting her letter to Pope Francis, Sophie sent a similar missive to Obama. In return, she received a letter from the president with a photo of the first family. Ever since, her parents said, she has dreamed of visiting the White House.

It is unclear whether Sophie will meet Obama face-to-face on Thursday, If she does, her parents say, she will try once again to plead their case.

"Her mind is very powerful, and her imagination is amazing," Raul Cruz said. "And we have always told her that if you have dreams, you have to do everything you can to get there. So she fights for her dreams."