But again, where has she been the last 3 1/2 years?

Good question. She was assigned the task of reducing flow to the border, not through it.

Harris was never the “border czar,” or put in charge of border security or halting illegal border crossings, as former President Donald Trump, Republicans and even the occasional media outlet have claimed. Instead, she was tasked in March 2021 with tackling the “root causes” of migration from the Northern Triangle and pushing its leaders — along with Mexico’s — to enforce immigration laws, administration officials said.

She focused her time and prestige on boosting private investment in El Salvador, Honduras and Guatemala, the so-called Northern Triangle; her goal was to help create jobs to bolster economies and dissuade migrants from making the perilous journey to the United States.

https://www.pbs.org/newshour/politics/kamala-harris-chose-a-long-term-approach-when-tasked-to-tackle-rise-in-border-crossings