Vegetarian Friendly Restaurant For Dinner
I can't think of anything in Anaheim, but Mother's Market has various locations in OC, and it has vegetarian and vegan options. They have a grocey store, and usually a cafe inside that serves food as well. www.mothersmarket.com
You might also look up some Indian restaurants in the Anaheim area online. (Certain regions of India have a predominately vegetarian diet.)
Hope I'm not too late...
There used to be a place called Lotus Cafe, and I believe they had a location in Anaheim - not sure if it's still there, though. Google shows one in Orange (very close), anyway. Try (714) 385-1233.
Don't know how far you're willing to travel - there are some good Vietnamese and Chinese places in OC - Au Lac in Fountain Valley is probably my favorite of the ones I've been to (though haven't been behind the Orange curtain in ages). I also like Alisan, also in Fountain Valley.
Native Foods in Costa Mesa is worth checking out if it's not too far, especially if you've never been to a Native Foods before. http://nativefoods.com/
I'd check out Happy Cow if you didn't already - http://happycow.net/