Mexico, like many other countries is well known for not allowing knitting needles on the plane. They may not take them all the time, but there are far more times they do than they don't. Not sure why she was upset, they were just doing their job.

While I don't believe you will find an official Mexican page that says you can't bring them, you will find page after page of knitters who had their needles taken from them at Security in Mexico.

Whenever you travel to another country carrying something that may or may not be allowed, a quick google search would usually show if you can bring those items or not. The knitting community is especially good about posting their experiences in their million different forums online.