The customer is NOT always right - in this case, she's absolutely wrong in the way she is treating this seller. Do not let her run over you. It sounds like she's having a very hard time right now, and while I am sympathetic, she has no right to treat you like that.
*I'M* pregnant, with two other kids, three shops on Etsy, one working vehicle for the two grown-ups in this house, a house to care for and myriad other things going on. EVERYONE has something going on. And yet I manage to still be polite and professional and as kind as I can be to everyone. When you get the items back, refund her the cost. If it's in your policies not to refund shipping, this might be the one time you make an exception.Every once in a while, it's worth it. :P
Good luck, sweetie.