One other thing I forgot to mention.....
By all means try to keep her in the dark about your activities and the extent to which you are involved in them.....
Case in point....A friend of mine, who often has to sneak away to be with his friends...played with us guys in a poker game a while back....cheap game, usually quarter or fifty cent game with 3 raise limit....his old lady finds him about 20 minutes after he got there.....just started berating him up one side and down the other....brought up issues about his mother-in-law helping with the business and money issues....she was seriously trying to embarrass him in front of us....a few of us looked at each other with that "what a cunt" look on our faces.....
As some have already mentioned about giving your gf or spouse a hundred dollar bill every now and then.....don't. When the two of you get to arguing, especially if it's gambling, she won't remember where that hundred came from but she'll remind you about some losses you took......losses that you paid from your pocket, not hers. When you win she will be up a few hundred, when you lose, the loss is all yours.
That hundred spends great but she won't remember where it came from or the effort that it took to get it in the first place....
Bottom line.....the less she knows about your enterprise the less it can come back to haunt you later, should you two ever decide to break up and things get nasty.....then she has all kinds of dirt to rub in your face, to your relatives or hers....IRS....government...police...you name it.....best bet small play it like you bet 20 bucks on a weekend, or better yet tell her nothing...