I'm sorry this is happening to you right before a big social event. A couple things come to mind:
1. No matter what happens--whether you attend or not--you do NOT need to tell anyone you have MS--just tell them you have a pinched nerve in your spine and have an appointment to see your primary doctor and/or physical therapist and/or chiropractor.
2. If you do attend the event, please be very careful and put your safety first, such as wearing flat-heeled shoes, using a cane, avoiding alcohol, not wearing a long dress that could cause you to trip, and ALWAYS holding onto someone when going up and down stairs/steps/curbs.
3. Call your doc tomorrow to ask for a quick appointment because you think an exacerbation is starting. Since foot drop is motor, your doc might want to consider steroids.
Best wishes, and I hope you feel better soon.