Welcome. If you want to learn more about Crohn's... especially from a patient's perspective, this is the place to be! I don't have the greatest of personal advice to give you, but I really am writing to commend your initiative here, and your heart for the situation. Your girlfriend is very lucky to have you.
I have had Crohn's for 8 years, and at first, discretion was very important to me. People knew i had Crohn's, but I talked very little about it and really downplayed details, symptoms, etc. I wouldn't call it ashamed or embarrassed, but I definitely was something like that. I didn't like the idea of discussing the terrible things involved with this disease... even with my wife.
Over the last year, however, I've been in a bad way, and decided that the best policy was to be frank with those closest to me. My wife has been a real trooper through it all, and I found that being able to talk openly with her is a HUGE relief. While she doesn't understand me as some around this forum might, she has a much better understanding than I thought someone that doesn't have Crohn's could.
I always felt like I was disappointing people; like I was letting them down, but I don't really feel that way anymore. Plus, it lets her help me and do things for me that are a major blessing for me on my worst days. From understanding small diet things to knowing when to say "no" to friends and family, something I need, or something I don't, that has made such a difference for me.
If your girlfriend is willing to talk to you about things, I think it can make you closer. Going to a CCFA seminar or reading up around here is a great start, IMO. Most of the stories at this forum are from patients who have IBD. You'll quickly find some of the common frustrations Crohnies encounter. It's certainly a more personal way to learn about the disease. Pamphlets and seminars usually give technical details, which are nice, but I like these forums because I can relate to the people. I understand the technical stuff, but I relate to the people, if that makes sense.