This was always the biggest thing about her that bothered me. She was his friend, and it would make sense that he would feel hurt and betrayed, even if there was no real logical reason to.

No it doesn't?

I think she had every right to say it, seeing as she had already proven her worth as a soldier. I understand that Shang felt betrayed by her lie, but still - at that point it was more important to act quickly and save the emperor from the Huns. And the only reason Mulan had needed to lie in the first place was because she was a woman, and she couldn't change that. So I don't see why he should have thought that she was lying this time.

I'm on both sides of the coin

While I think that Shang was more bothered by her lying than her being a girl, she was right, nevertheless. She had won his trust as Ping, as soldier, so he should trust in her when she acts as a soldier.

I agree with Swanpride

It was a bit of both, I think. But it's kinda stupid, only a really twisted person would lie about the Huns surviving and coming to kill the Emperor. He should have believed her.

At least he learned his lesson in the end, a woman is always right dammit! =)