Tell her something alike: that you understand her and that she should kindly remind you, when being too loud is the case, because it's not your intention to bother anyone. That might be the most easy resolution to get along. Such territorial issues (exactly alike some may have them with their neighbors) always bring up the aspect, of who was there before (even if no regulations would catch, but HR might wish for a certain harmony)... beside that, I can only tell from experience, that having to actually program besides someone who performs loud phone calls is close to torture.