First work-related party being vegan...

My boss is throwing a belated holiday party for us on Thursday and she's ordering in from a pizzeria.  I heard her ordering pizza and wraps.  She doesn't know (or care) that I don't eat meat/dairy/etc.  I don't know if I should say something or just eat something beforehand and not eat anything at the party.  I don't want to look anti-social, but I hate talking about my choices to her since she can't understand why I won't eat meat since she loves it.  That's what she said the last time I told her I was a vegetarian.  Now she really won't "get" that I'm vegan.  NOT that I care about her opinion, but I hate having to defend my decisions.  Maybe I'll just write her a quick email tonight from home telling her and be done w/ it.

**edit ... I emailed her and told her about the food issue and she said that there will be a cheeseless pizza.  I'm going to call the place she's ordering from to find out if they use any meat in their sauce.  So, it looks good so far!