Sometimes I think it's the tone that really irritates people. Sometimes people phrase things as "you should do this," when what they really mean is, "I wish I'd done this/I'm glad I did this," and sometimes you can tell that from their tone. Makes it a little more palatable, I think.
And the duration of the conversation can be important, too. Imagine if she'd started talking as you were getting on the elevator, and had kept harping on the subject and pressuring you to agree during the whole ride! That would've been unpleasant.