I say our spouses need some amount of privacy. We my have married them, but they are still entitled to their own life. With that being said though, that doesn't mean you aren't allowed to be concerned or question their behavior. If your spouse gets incredible defensive and refuses let you even look at her phone, it would send red flags off for me. I would talk about it if possible. Ask her why she doesn't want to let you in on who she is contacting.

Dealing with a similar situation myself, my wife would do the same thing. Get calls and not answer them when I am around. Hide what she is saying to people on skype when I walk by. My wife was caught up in having online romances, and sharing far more than she should have. Needless to say, it is hard to fix things when a spouse violates your trust. I don't look at her the same anymore, and I question whether I want this to work, not knowing if she is going to be there for me.

I would start by talking to her. She could have a good reason she doesn't want to share, or she really could value her privacy and there is nothing wrong. I don't think there is anything wrong with some privacy, as long as there is still trust. For me some signs that there was something going on, where that she would become distant with me. I would try to show her affection and she would get annoyed. Best of luck to you. This is a difficult spot to be in. I hope things work out for you.