So does the phrase "Mother of my Lord" (Luke 1:43). Accepting for the moment your Nestorian premise that there were two Jesus, which one was St. Elizabeth referring to, the human Jesus or the divine Jesus?
Peace be with you
*Mother of GOD* does not show up in Scripture.
The problem with that verse is that we don’t know whether Elizabeth was meaning “master” or “a person exercising absolute ownership rights; lord (Lord), or something different. The word used was kurios for which several interpretations can be found here: http://biblesuite.com/thayers/2962.htm
Using that verse without the whole of scripture is useless.