How would you handle this situation (work related)

So I work midnight's at the local hospital. My co worker who is my relief at 630 in the morning keeps strolling in 5 minutes and up to 15 minutes after I'm supposed to leave. Which wouldn't be a huge deal except my husband waits for me to get home to our kids.(luckily it only takes me 7 minutes) to go to his job. He works about 15 to 20 minutes away so if I'm able to leave right at 630, he gets to work on time, and all is well.

I've asked her to please just get there on time so that this isnt an issue. She did good for a bit, but today she rolled in at 641, I clocked out at 642, flew home as fast as I could, my husband was so mad and he was late for work and got in trouble. I dont want to take it to my manager because it's so petty and I hate to be THAT coworker, but it's a pretty big deal since he's the breadwinner.

Should I talk with her again or should I take it to my boss?