G'day and welcome,
Being a female won't be an impediment to flying in Australia.
There's a couple of things you can do. Firstly, check out the AWPA website, they do have scholarships for female pilots (and some scholarships open to both sexes).
AWPA You can do maths and physics bridging courses that QF recognise. Not the cheapest but they are over in weeks rather than years. If I were you, I'd toddle over to Tech and do their course. They are pretty good. At the moment, a degree or diploma isn't essential to be a pilot in Oz. You can pick up a degree once you are working (been saying that to myself for years. One day I'll do it!) and you'll get credits for your aviation study.
Remember, all that is officially recognised by CASA is your CASA licences. A degree isn't recognised by them.
Your age is not a problem, the earlier you start the better really. Gives you more time to get to where you want to go. You can't hold an ATPL before 21 any way.
Good luck