Although the 17-year-old Kaiser High School senior carries a 4.09 grade-point average and has been accepted to the university, she cannot apply for government loans because she's an illegal immigrant and doesn't have a Social Security number.
"I don't know how I'm going to pay for school," she said. "All I want is a chance."
Castro said less than a year ago, one Kaiser High administrator refused to sign a petition supporting federal college aid for illegal immigrants, supposedly saying that they don't deserve to go to American universities.
"I just started crying," Castro said.
Some say Castro has spent her
"California has already dumped $100,000 in free education (on her)," said Robert Rector, a senior research fellow at the Washington, D.C.-based Heritage Foundation, a conservative think tank. "If you want to be tough about it, you can ask for it to be repaid."
Castro smiles wide and talks fast when asked about her plans to major in political science at the campus she has visited three times.
But the reality of having to pay more than $30,000 in fees per academic year often quenches her enthusiasm to the point of tears, leaving her to ponder a future without a college degree.
When she was 8 years old, her family fled the crime and violence of their hometown in Jalisco, Mexico.
Two of her relatives were kidnapped and murdered, and when the family stopped at her uncle's house in Tijuana before illegally entering the United States, he warned them not to go near the windows because of the frequent shootings in the neighborhood.
Castro cannot forget the stories told by childhood friends in Mexico, who spoke of the dead bodies they would see in cars after a bloody street battle.
"It's not something a child should have to see," she said.
On her first day of school in the U.S., Castro's third-grade class made Native American dreamcatchers, sacred ornaments believed to allow only positive dreams to enter one who is sleeping.
She quickly tested out of an English-learners class.
Her schedule in high school has been laden with advanced placement coursework.
Castro joined the Army Junior ROTC in 2007. She's been a member of the National Honor Society and a president of the Advanced Biology Club.
And, until recently, hardly anyone at the school knew she was undocumented.
An evangelical Christian, Castro would ask the campus Christian club to pray for her situation, the request couched in vague terms so as not to let on about her status.
Her mother works in a barber shop, and her father is a house painter struggling to find employment. A year of Berkeley costs more than what the family makes annually, Castro said.
"I know there is a God, and I know he's my father, and he loves me, and I know he has a great plan for me," she said. "He's opening doors for me that I can't open by myself."
Some undocumented students have already walked through the doors of American colleges.
Sergio Hernandez's family came to the country illegally when he was 2 years old.
Now 23, Hernandez is set to graduate from Cal Poly Pomona with a bachelor's degree in political science. He plans to pursue a master's degree in higher education.
"I understand how she's feeling, because she feels like her dreams are closed, and she's not empowered," he said.
Hernandez, a former class president at Rosemead High School who has either joined, led or started numerous Latino associations at Cal Poly, said he has been able to pay for his school because of AB540, a law passed in 2001 that allows illegal immigrants who graduate from California high schools to pay in-state tuition at a state college or university.
His father owns a landscaping business and financially assists Hernandez, who also works at the school's Cesar E. Chavez Center for Higher Education.
Hernandez in his first year of school used private scholarships to fund his studies. He said such scholarships are great ways for undocumented students to get the financial aid they seek to attend college.
And he, like Castro, supports the federal Development, Relief and Education for Alien Minors Act, also known as the Dream Act, that is working its way through Congress.
The bill would aid about 65,000 illegal immigrants each year who graduate from high school and meet other requirements.
Under the bill, illegal immigrants who entered the U.S. under 16 years of age and have lived here more than five years, graduated from high school and can demonstrate good moral character may apply for conditional legal status.
They would be allowed to stay in the country for six years under such status.
Students can convert their conditional status to permanent residency by graduating from a two-year college, studying at least two years toward a bachelor's degree or serving in the military at least two years.
Students receive green cards and could apply for citizenship, if the conditions of the probationary period are met.
"I've been fighting for the Dream Act ever since it was introduced," Hernandez said.
Castro has worked with Latino activist groups such as the left-wing Coalition for Humane Immigrant Rights of Los Angeles to gain support for the proposal.
"A lot of people see us as criminals," she said. "I don't see myself as a criminal. How am I a criminal at 8 years old, when I had no control over my life?"
Rep. Joe Baca, D-San Bernardino, agrees.
"It is wrong to unfairly punish those young people who come to America through no fault of their own," Baca said.
He supports the Dream Act, but said it is limited in that it helps only those who are seeking assistance in higher education or those who enroll in the military.
He has introduced the People Resolved to Obtain an Understanding of Democracy, or Proud Act, which would give "responsible immigrant high school graduates" a realistic pathway to citizenship if they have good grades, show an understanding of U.S. civics and "stayed out of trouble."
"The good news is the comprehensive immigration bill introduced in the House, H.R. 4321, includes provisions of both the Proud Act and the Dream Act," Baca said.
Rector disagreed, saying such bills do nothing more than reward illegal behavior.
"There are probably a billion people in the world that would like to come to (the United States)," Rector said. "We're saying we'll confer this on a few thousand people precisely because they broke our laws."
Rector said the Dream Act encourages future law-breaking because it has no sunset date and gives illegal immigrants that much more incentive to cross the border.
Paying for the education of undocumented children and effectively granting them citizenship so that they in turn will request legal permanent status for their parents essentially transforms the U.S. into a ruinous "global open primary" for lawbreakers who eventually will vote in the country's elections, Rector said.
A child benefitting from a criminal act such as crossing the border illegally is inexcusable, he said.
In fact, he suggested an alternative.
"They need to go back where they came from. That girl would do quite well in Mexico. It's not like consigning her to hell."
Castro said she hears that type of rhetoric all the time, from conservative political pundits to Tea Party activists.
"All I want to do is go to college," she said. "I feel as American as anybody else."
In lighter moments, Castro jokes that she could wash cars to raise money.
In the meantime, she plans to attend Riverside Community College in the summer and fall while she figures out how to pay for Berkeley.
"I don't want to fall behind. As much as you explain it to people, no one understands. It's not an easy journey. Everything I have is in the United States."