I'm a vegan.
A person who eats chicken once a week and chows down on pastries that are full of eggs is not a vegan.
Therefore, in this scenario, you are not eating with a vegan. You are eating with a person who decides day by day depending on how her mood is, what 'diet' she's on today. So, IMO, you are not obligated to cater for especially for her 'just in case she's vegan today'.
As a vegan, I would still be ok at your gathering eating the veges and (probably) the pita. As far as I'm concerned, that's fine. I recognise that not everybody is a vegan and I always manage to find something to eat! If a host goes out of their way to provide a few vegan options, then I think that's just the coolest thing ever! A lot of the time, my friends and family will pull me aside at their party and say 'this and this and this are all vegan, enjoy!'. They don't make separate food for me, they just point out the things on the table which are ok for me to eat and, honestly, that's more than I would ever expect - I think that's great!