Six years ago, when Jen Fox was 19 and planning to go to college, she slammed her finger with a car door. It hurt like hell and she went to the UMass Memorial Medical Center in Worcester to get treated.

While she was being examined, she asked the doctor in the ER to check a lump in her neck.

Her primary care physician had looked at it a month before and said it wasn’t big enough to worry about. But the lump kept getting bigger.

The ER doc was dismissive, saying it was nothing. But Jen Fox didn’t like his condescending attitude, so she asked to see another doctor at UMass. That doctor wasn’t dismissive at all, and promptly sent her to a surgeon, which probably saved her life.

She was diagnosed with Hodgkin’s lymphoma and began treatment at Dana-Farber Cancer Institute in Boston. Because she got sick, she couldn’t go to classes full time and so lost her student insurance.

But, luckily, the Affordable Care Act had become law a year before she got sick, so her parents were able to cover the costs for her care with their insurance.

After her treatment, she went back to school full time and in November 2012 she had her one-year scan. The cancer was back.

Again, the Affordable Care Act made all the difference. First, she couldn’t be denied coverage because of a preexisting condition. Secondly, and this gets lost in much of the debate about the Affordable Care Act, the stem cell transplant she needed was covered because the ACA prevented arbitrary lifetime dollar limits on treatment.

By the time she underwent the successful stem cell transplant that saved her life, she had racked up bills that were probably double the previous $1 million treatment limit.

Given that Jen Fox would be dead or, at the very least, dead broke without the Affordable Care Act, she is understandably defensive of it and worries about President Trump’s pledge to repeal and replace it with something he claims will be better.

On Tuesday night, when the president outlines to a joint session of Congress what he is going to do to the Affordable Care Act, Jen Fox will be sitting right there in the House Chamber, listening to him.

Fox, a Hopkinton native and now a student at George Washington University, is an intern in the Washington office of Representative Joe Kennedy, who like all members of Congress gets to bring a guest.

Kennedy couldn’t think of anyone better suited to bear witness to the importance of the Affordable Care Act than his intern. She’s been cancer free for almost four years.

It is slightly ironic that her last name is the same as the network whose pundits have done as much as anyone else to persuade many ordinary Americans that the Affordable Care Act isn’t good for them.

“I think a lot of the people who say the ACA is not working, or say negative things about it, don’t necessarily know what it is or what it does,’’ Fox says. “Maybe they don’t understand that people get sick and sometimes it costs hundreds of thousands of dollars or even millions of dollars to treat them.’’

“I hope it’s that they don’t know,’’ she said.

“I hope they don’t think people should have to spend their life savings or die if they have no savings. We’re talking about people’s lives.’’

She wishes she could talk to the president.

“I’d tell him that I’m not an exception to the rule. There are 70,000 young adults diagnosed with cancer every year, and they’re young and healthy and might not think they need health insurance. I wish he could meet someone who has to make a decision between paying the mortgage or paying for their child’s health care.’’

Jen Fox knows better than most that the Affordable Care Act saves lives. The fact that she’s still on the right side of the grass is not about partisan politics. It’s a preexisting reality.

Kevin Cullen is a Globe columnist. He can be reached at cullen@globe.com.