I like INFPs so much I married one.
My INFP husband has an INFP mother. 100% 'F', from what I've observed. She's a walking raw nerve ending. I really, REALLY have to keep it under wraps when we visit his folks - she visibly *flinches* when I make (what I consider to be) a slightly outrageous remark. Like Ruthie said, she's pretty darn good at reading people - and very naive (like my DH).
Oh, wait, I was supposed to be talking about my romantic relationship w/ an INFP...it's fabulous, just as long as I keep remembering he's an INFP.