Important survey!

I have a question for all bloggers. I'm currently having a bit of a moral dilemma and I could use your help. Girlfriend does not know that I have a blog. It's kind of my personal little thing and I like it that way. It's my place to vent, share, express myself, etc. without the eyes of those in my life. We had a long talk about not keeping secrets this weekend because my altruistic intentions of keeping health problems from her REALLY hurt her feelings. I shared, she understood, all is well with us, but it got me thinking about my blog. It's not hurting her, or our relationship, by hiding it from her. Should I feel obligated to tell her about it? Is it fine to keep this just between me and those of you who read what I write each week? Am I trying to justify my actions? Absolutely. However I would really like your input, especially those of you who have a blog-do your significant others (or family members) know about/read your blog? If yes, how does this affect what you write (i.e. do you censor things or run it by them first)?