One thing often neglected by people making the innitial switch to becomming a vegatarian (or vegan, or purist, or whatever) is that the easiest form of digestible minerals vitamins come from uncooked fruits and vegetables. For the 'optimal' (note that there is not such thing since dietary requirements vary for each person over the course of a day, week, year, lifetime) diet, you should only eat a small amount of cooked foods each day (perhaps 15%-25% of your dinner or less). Bannannannannas cannot be stressed as a good multi-vitamin, along with several glasses of carrot juice each day. Staying away from your three whites is perhaps the best thing to look at as far as what not to do: white sugar (bleached and processed to a nearly non digestable state), white flour (bleached out most major sources of vitamins from the grain), and white fats (meaning animal fats from meats, poultry, fish, some butters).
BTW, as a previous posters commented, ditching the diet after a few months can have some very negative effects for a lot longer than just a few days on the jon. You effectively alter the levels of probiotics in your intestinal tract. These probiotics aid in reclaiming digestive and bodily fluids and the kinds that feed off meat by products are very difficult to get back up to normal levels (in that it could take a year or so for them to attain standard levels). During that time or adjustment, you may feel sick often with minor flue-like symptoms since your digestive track is in a whack.
(Edit): BTW, changes in ones diet ultimately effect no one but yourself. Make sure that if you want to alter your diet, its because you want to better yourself and not make some kind of privatized and localized message that somehow you hope will reach the world over. Sorry to say, but it won't. Make sure that your gf understands this since its her health she's ultimately playing, harm to which is not worth the minor message of "save the fill in the blank".
(Second Edit)
Plus, we were all naked. Bonus!
Err . . . that depends on who your looking at. Bodacious member of the opposite sex? Yeah! Bonus galore! 50 year old hick with more body hair than the missing link? I'll take civilized life for 100.