Would you feel offended if one of your 'close friends' told you that they kept parts of their life from you?

Well, one of my ‘close friends’ (for years now) had just mentioned today that she has certain parts of her life where she hides from me. She didn’t exactly say it like that, but it still made me sad =(. She said “I’m glad I have guy friends to talk to stuff about, I can mention things that I would never mention to you guys ever! hahah”. Something along those lines anyways. She’s also mentioned something like that this year as well. About how she tells different friends different things about her life… I don’t want to know only a piece of her life, I want to know everything =\. She also said something like “There’s a lot of stuff you don’t know about me, hahha”

I always believed that friends never hid things from their friends, and that they showed every part of them self around their friends.. Regardless of sex, I pretty much act the same to all of my friends. I don’t hide anything, even if they have nothing on a particular topic in common. I just talk about my life and stuff.

… It kind of feels like she’s ‘fake’ sometimes. She’ll say one thing to another friend, and another opinion to me…. so… what is it? Which is her honest opinion? Does she just say things to make the person happy? I don’t understand, and it really frustrates me.

Am I right to feel offended? Do you hide certain things from your friends…. or do you let them know everything?... And, is there anything that can be done?