Catholics believe that there are three and only three divine persons. God the father, God the Son (Jesus) and God the Holy Spirit. Catholics also believe that these divine persons are Co-eternal, meaning that they all three exixted from the beginning of time and they are co-equal in stature to each other and only each other. We also believe that Jesus from the moment of his "Conception" came to posses a second human nature. This nature is Co-Equal to his Divine nature. By that I mean that He is Fully God and fully man/ human at the same time.
Mary gave birth to this one person with two natures.He fed at her breasts and she even changed his little diapers. So yes we believe that she is the "Mother of God."
I hope this clarifies our belief
Ummm, v, MarMema is an Orthodox Christian. From your seminary days you may remember a little get together called the Council of Ephesus where we Eastern Greek speaking Christians, lead by +Cyril of Alexandria in opposition to Nestorius of Constantinople and John of Antioch, taught a bunch of heretics, including an emperor, how to pronounce "Theotokos". Marmema knows quite well that Panagia is the Most Holy Theotokos.