they claim to have vegan substitutions. Also Naf Naf would please a vegetarian, they are in Naperville. Not very dinner like though.
The Ivy has a few vegetarian choices like butternut squash ravioli, etc. I think one could eat well there.
Also Macaroni grill you can get pick your own pasta with pesto or plain marinara sauce. Or fettucine alfredo. Of course it all depends if your friend is vegan or eats fish or eggs.
I think any of these places would have something for everyone.