shark 1963, food is the one and only important thing for any Thai girl besides her parents. It will be worshipped and eaten in great celebrations all day long, every day.
Doing the same with German food will create a Farang-sized ugly witch, so see the good side of it
However, even in Germany it should not be very difficult to get all the ingredients, as you can buy the fish sauce, chilis and the rice at an Asian (or even specialized Thai) shop in bulk and it will keep for a long time; the Thai food they eat normally is not very sophisticated and with simple ingredients.
If you do not know any shops in your neighborhood, it should not be very difficult to find people with Thai spouses within a radius of a few km from your home and they can help you with directions; from my experience, there is an incredible number of Thai girls in Germany. Also a good place to ask would be German courses at the next Fachhochschule, participants there should be able to help you on.
Beware however, together with good advice your GF might very easily pick up a lot of bad habits (like gambling) from them as well, so keep an eye on it; also an experience, luckily not a personal one...