Find the issue she cares the most about -- healthcare? the environment? police violence? -- and point to specific solution already-elected progressives are pushing. This cuts through the doubt of "well you could never get in power saying that" and the apathy of "no one seems to be offering a real solution."

Next, make that issue her red line. It's not enough to love candidates with the right position on that issue and kind of be OK with candidates who oppose it; candidates who oppose it are bad, because this is a big deal that has major impacts on people's lives.

Then, if you haven't already, get her going on media analysis in the style of Citations Needed. It'll all click real fast as she'll see the bias against her new red-line idea.

Finally, point out how the capitalist media that's propagandized her red-line issue has propagandized American foreign policy. Point out how socialist states -- Cuba is usually the best place to start -- do her red-line issue better than the U.S. (note that Cuba is still not great on incarceration even though they and every other country on the planet imprisons fewer people per capita than the U.S.). Get into the "what should we actually think of socialist states?" conversation, which is liberalism's final boss for many.