I am half German and half Spanish, so I think Inez would be a pretty name to give to a daughter to reflect my Spanish heritage. Oddly enough I had a great-great-grandmother named Inez, but she was on the German side.
The Spanish form of Agnes is Inés, not Inez. Inez seems to be an adapted foreign version. In Spain this name is very rare. According to the Instituto Nacional de Estatística, 31 women in Spain are named Inez, 25 of whom are foreigners, mostly from Brazil and Poland.