Hi, We have, here in France a lot of TV broadcast related to the problem your sister in encountering( right ?) and the problem she is facing is not only the religious ethic is also the legal situation the child will have when that child reaches his or her majority. and the right for anybody to search for the identity of is biological parent. I do no the reason she wants to do it "alone" but her child will be told and taugh that to be born, a mother and a father are necessary ! and here start the psychological problem that the child will have to face or live with (good or bad, we all have our reason ) I was, once sincle MOM and never forbid the father to see his son, because at a point it is very very important for the child to have marks to know where he or her goes. after watching tons of those tv broadcast or reading on the net, those children can have a normal life if they are prepared, but noone can tell how long, and how do we know really if they are "fine" their head might say "yeah, I 'm fine, life is great" but their heart says the contrary...here in Europe, it is only possible in Belgium or Netherland... because there, the gay and lesbian community is more "free" than anywhere else in europe, then they always find a solution.
I don't know if that answer a little bit to your question. but I've tried.
BTW : is Perth in Australia ?