"Crazy" has a problem with its use when you're talking about people with problems. It's imprecise and tends towards a universal claim about the person's qualities. It's natural to defend a friend called "crazy," because you don't know how if the speaker is extending the definition to things that you consider functional. Recognizing those functional parts is really critical for a friend who's a bit disturbed in other parts, because it's those things that 1) have a tendency to be overlooked, distorted, or diminished by the troubled person and others and 2) hold the ways in which the person can get better. Moreover, I think this murkiness that starts the struggle between words like "crazy" and what someone thinks about their troubled friend has a tendency to compound itself, as both sides of the conversation, in the course of the conversation, set up precedents based on the miscommunication, so you find yourself being accused of positions you don't remember taking, and trying to articulate a defense that has to grapple with first explaining how you've been misunderstood. I don't know the exact situation, but she might have ALWAYS defended her because the entrenched history of the conversation made it increasingly difficult not to.

I don't know if this is useful, but I figure it's a frequent enough problem that it bears some analysis.