I like Women's E-news. I get it in my e-mail, but it's also on the web so I've supplied a link.
Short form: women (and men) often hide money from their significant other. Women often do this because they've been in a relationship with an abusive and/or financially irresponsible partner.
About a decade or so ago, I read two separate books on the specific subject of equality in heterosexual relationships because I had a lot of questions about how couples handle money, chores, etc. and talking to people was just confusing me -- I needed some organizing principles. Between the books and the talking-to-people, I decided that (a) the way people manage money says a lot about their relationship and (b) you won't ever see me with only joint accounts again. Well, maybe when I've lost a competency hearing and someone else is managing the funds, or maybe if everything's been signed over to the grown children because I need to qualify for state needs-based aid or something. Not before.
It's all well and good to trust someone. It's much better to be able to make and implement important decisions yourself. And it is unutterably important to make absolutely certain that a lapse in judgment associated with a significant other does not become a tragedy. I firmly believe that if you're with someone who demands a level of trust incompatible with independent action, that person is, prima facie, a Really Evil Person. You should definitely hide money and resources from them, even if you can't bring yourself to leave right then and there.
You might or might not be able to imagine my response to the above linked article. Let's just say I'm seriously contemplating canceling the e-mail subscription to Women's E-news. Do _not_ _ever_ _ever_ interfere with women's mad money.
Good goddess. What the _hell_ were they thinking?