If I am honest given this involves a posting overseas I would be concerned about whether it's too risky an investment. I expect that's the wrong answer.....although frankly I'd feel the same if it were a man proposing to move his wife overseas if planning a family
I am betting she'd have a case for discrimination if I asked and then she did not get the job. By the way I have no idea if she is or isn't!
I am a very small company by the way (not that this would impact the legality!)