The nose-ringed geography student led millions into the streets since 2011 asserting the right to free education. Highlighting a generational shift in Chile's traditional politics, Vallejo and three other student leaders in their twenties were elected to Congress on Sunday.
Despite mass protests that raised hopes across Chile for deep educational changes, the system still fails families with poor quality public schools, expensive private universities, unprepared teachers and banks that make big profits on pricey loans.
But the 25-year-old Communist Party member said Thursday that she's confident Bachelet's coalition will have enough seats in Congress to achieve educational reform.
"Given the result of the elections, we have a majority that allows us to make structural changes," Vallejo told foreign correspondents in a meeting. Next to her was Karol Carolia, another student activist elected to Congress.
"Social movements are pressuring many sectors that were not in favor of change before and that have now changed their mind," she said.
Bachelet, who became Chile's first woman president from 2006-2010, nearly doubled the votes of her conservative rival, Evelyn Matthei, in the first round of the vote.
Vallejo said the run-up to the vote will be major challenge as they race against the clock to convince others to support the education reform that she fought for in the streets. But she said she's confident that Bachelet and her coalition will score nothing but a "rotund victory."
Bachelet, a 62-year-old socialist pediatrician and former political prisoner, has vowed major changes in taxes and education and a reduction of Chile's sharp income inequality. Her Nueva Mayoria coalition already has the votes in Congress needed to raise taxes, but lacks the super-majorities to change the dictatorship-era electoral system and constitution.
"Many sectors say we won't be able to makes these changes because we don't have the votes in Congress but we've learned that there's no limit to what the social movement can achieve," Vallejo said. "It's not about using a calculator and seeing how many votes are missing."
Chile, the world's top copper producer, is seen as probably the best managed economy in Latin America because of its strong growth, low unemployment and solid institutions.
But critics say policies launched under the 1973-1990 dictatorship of Augusto Pinochet continue to block urgent social reform and foster social exclusion and inequality.
Schools in Chile were free before Pinochet pushed privatization and ended central control and funding of primary and secondary schools. Public education in poorer districts suffered even as a voucher system directed billions of dollars in public funds to privately-run high schools.
Today, Chile's higher education burden is the toughest of nearly any nation surveyed by the Organization for Economic Co-operation and Development, or OECD. While families in Scandinavian countries pay less than 5 percent of the costs and U.S. families pay more than 40 percent, Chilean households must pay more than 75 percent from their own pockets.
Many Chilean families quietly bore the burden for years before student activists gave them a voice two years ago.
Widespread marches regularly paralyzed Chile's major cities, drawing international attention to student's demands to change the tax system so that the wealthy pay more, and put the state back in control of the mostly privatized public schools.
"We were elected because Chile changed," Vallejo said.
Luis Andres Henao on Twitter: https://twitter.com/LuisAndresHenao