Why are women so insecure?

Last night I was mortified when my brother's lady of a few years showed up at the strip club we were at, having libations with a trio of potential investors we were hosting who were in town from Vegas. She made a scence and embarassed my brother, myself and our three guests. Going so far as to call two of the dancers sluts(whom by the way were not sitting with us, but were minding their own business with a guy seated behind us.) she stormed out with my brother following close behind. So today, after spending all night fighting with her he and I were talking and he was looking for counsel. She felt he had no right to be in a strip club drinking (even though it was work related..and the entertainment group we are partners in have a quarter share of the strip club we were at) and that he was disrespecting her by looking at other naked women, and she questioned his loyalty. This really hurt his feelings. My brother is director of operations for our nightclubs and lounges and his persona fits the role. He is precise, perpetually responsible and generally a stick in the mud. He does not party, he does not cheat, I cant even get him to get drunk with me but once a year. She said last night "birds of a feather flock together" in refrence to he and I. She does not like me at all, her being far more conservative like my brother is. She thinks because I drive flashy cars and date kind of trashy girls, somehow my brother is secretly longing to do the same. There is nothing further from the truth, and if she could see how he is (I dont allow spouses or girl friends into our establishments, which has long pissed her off. But your wife cant hang out at the office if your an accountant, why should it be any different in this business) she would understand how damagaing to their relationship her actions were. I told my brother to leave her, but now wonder if it is based on the fact that you should never waste your time on any woman that insecure, or if it is because I love my brother and am legitimately insulted that such a loyal and honorable person could be treated and embarrassed in such a fashion. Did I give him the right advice? God knows I am not the king on sucessful relationships.