I agree with the others who say that you should talk to her or to the friend who invited her. I also agree that you don't have to make her a special meal, but it would be sweet of you if you did.
I don't know where you live, but if you are not near a big city, it might be hard to find vegan sides/entrees at the deli counter. There are lots of what I call "hidden meat" ingredients that not all deli counter workers are aware of. If you are buying an asian dish ready made, make sure to ask about fish sauce, oyster sauce, bonito flakes, and any other seafood products. If you are buying something typically western, check for margarine, whey, cream, butter, milk, mayonaise. With lots of deli workers you have to specify each and every one of those, because if you just say "dairy products" they might forget that whey comes from milk. There is also an enormous list of food dyes and preservatives that come from animal products as well.
If you do decide to make her a special meal, here are some ideas for quick and easy things you can buy, that are not likely to have any hidden "gotchas", to whip up a vegan meal with very little prep time.
Jullienned veggies with hummous or tahini
Spiced olives from the deli counter served with tortillas or syrian bread (Check the ingredients. Most flatbreads only contain flour and water and preservatives, but some contain whey, margarine, or butter)
Corn tortilla chips (again check the ingredients for whey, margarine, or butter, but these are typically okay) with salsa.
Storebought french bread/bread rolls are often vegan. Ingredients to look out for are, again, whey, margarine, butter.
White rice. If you are really ambitious you can saute some onions and frozen peas in olive oil then toss them in.
Most storebought flatbreads
Stir fry veggies
Spinach and pinenuts sauteed in olive oil
Spaghetti (check the ingredients on the box for eggs and whey, but many brands are vegan) with tomato sauce.
Portobello mushroom sauteed in olive oil, served on a multigrain roll with burger fixin's (lettuce, tomato, red onion, mustard, but check the ingredients first).
Keep some of the greens reserved before you add th ceaser dressing to the rest. If you don't already have a vegan dressing in your fridge, you can whip together equal parts balsamic vinegar and extra virgin olive oil, with a splash of lemon and some dried rosemary.
Most citrus sorbets are vegan, but you might want to check with her to see if she has an aversion to refined sugar. Since refined sugar is filtered through charcoal made from bone, many vegans won't eat it. If you have a health foods store or Trader Joes or something in your town, you can find sorbet/ice "cream" labled as vegan friendly.