Hard to say when you would draw without being there, but if you wanted to deter without brandishing and you carry OWB covered by a jacket or outer shirt as I do, then simply turn the gun side toward them, sweep the outer garment back and make a big show of adjusting the holster. 99.9% of thugs at this point will get scarce. If they are innocents you may get a funny look but they likely won't totally freak like they would if you drew. Of the other .1%, they might initiate a fight with you. If so, you are ready. Your hand is on or almost on your weapon (my thumb break would have been unsnapped long since, at the moment I thought I was being shadowed) and you can pivot to cover your girl and address the threat. Hopefully you will, at the least, soak up any lead intended for her and stop the threat. Best case, you stop the threat and neither of you is injured. Of course, if she carries, you can fight as a team.
I consider those who cause innocent people to be defenseless through advocating and enacting "gun control measures" to be murderers by proxy.