Dollar General upset im not cancelling my thanksgiving

So I work in Dollar General while i go to Is college. I made sure to put in a month ahead that I cannot, nor will not work thanksgiving becasuse I was going out of town. Manager approached me yesterday saying "you will be coming in that day or you'll be written up. But because im nice ill let you decide between dayshift (7am-4pm) or nightshift (4pm-11pm.)" I explained I followed the steps required, I marked it on the calendar and put as such on the app we use. She then responded with "thats not how things work here, now dayshift or nightshift?" I plainly told her "if you schedual me for that day, and you're understaffed thats your fault because im not coming in that day, my life isnt work" (Apologies for grammer, english isnt my first nor my best language)

Edit:spelling and punctuation Further context: manager expects everyone to work that day except her husband who has the day off. We get paid $10 per hour management makes $15 (usd). I will update more if anything happens.