Dayum! I'm glad I'm not married to some of you guys! My husband decided a few months ago that he wanted to do a cycle, and since I didn't know shit about gear I found my way here so that I could research what he was getting US (yes, US) into.
Quite honestly, given that it is illegal here, I would be fucken PISSED if he got our family involved in gear without giving me a chance to research it and decide if it was a risk I was willing for him to take.
Now, if it's just a GF, and she is not put at risk by your using (ie: you don't live together, have kids together, etc) - then it's probably best to keep it a secret. Women are indeed scandalous when they want to be.