"one may assume"? You know this, how?
Elizabeth addressed her as "Mother of my Lord". Sounds a lot like "Mother of God" to me.
an obvious association to the pagan Ishtar
Really? So when pagans apply a title to one of their "gods," any subsequent use of that title by Christians is somehow "pagan" ... by "obvious association"?
The Greeks called Zeus "heavenly father". Guess calling God "heavenly father" is "an obvious association to the pagan Zeus," by the same logic you're applying.
After all .. we ARE related through Adam and Eve ... right?