I don't know my spouse's PIN and she doesn't know mine. I use her computer sometimes. We trust each other, and have a really good relationship.

I think it's perfectly fine for partners to have private conversations with friends &amp; family.  I don't have any need to have her phone PIN. That's hers. She's a separate, autonomous human being and deserves a bit of privacy to vent to friends when she's annoyed with me, or whatever. I have no problem with that. 

Different strokes and all that.