I think it would almost definitely be shortened, especially in Australia.
Even if you managed to get it not shorted in her young childhood, you'd have to be prepared for her choosing
Emmy or
Ellie herself one day. I'd imagine the most likely everyday and 'natural' shortening of it in Australia would be simply '
Em' and you'd have a pretty impossible time preventing that one. As an aside, I really quite like
Em. It's much better than
Emmy or
Ellie!
I like the sound of
Emmanuelle but it is way too obviously religious for me to ever consider myself. I would definitely assume that anyone who used the name for their child was religious.