One of my coworkers is accusing me of getting out of attending Open House? How can I get her to stop nagging me?

I have a coworker that isn’t too fond of me and she has been nagging me about me not attending Open House as it’s mandatory. I’m also a student in college so that’s also my priority. My school work is so important and I have a lot to do tonight. The admin and my two other coworkers understand and told me to do what I have to do. If I don’t work on my assignments, I’m going to fall behind and then I’ll be piled up with even MORE homework and I have a lot to do on Friday also as it is. My nagging coworker said I should have gotten a head start and I did with the earlier assignments but I don’t wanna overwhelm myself. She said I’m going to get fired and regret it.
Should I feel bad? I have four assignments due tomorrow and I was working on an assignment that was due Monday and last night.