Sorry to hear your partner is going through this. I won't try and canvass everything you need to know about family law as much of it will be irrelevant unless this matter proceeds to court. Hopefully, it won't have to go that far.
Parenting matters aren't governed by law unless parents are unable to reach agreement and ask the court to intervene. Contrary to popular belief, the Family Law Act 1975 doesn't impose any rights or obligations on parents, but rather, it imposes obligations on the court as to how it determines an outcome for parenting disputes.
The most significant part for your partner at this stage, however, is section 60B, which holds that children have a right to know, spend time and communicate with both parents on a regular basis, regardless of whether the parents are married, separated, divorced or any other manifestation of relationship status.
Thus, the child has a right to have a relationship with his/her father.
The first step in ensuring the child's rights are upheld is to organise a family dispute resolution conference with the other party. Family dispute resolution is a mandatory step before any court proceedings can commence. It is an alternative resolution pathway whereby the parties meet in a mutual setting to discuss and try and reach agreement about parenting matters, and is governed by an accredited family law mediator, who acts as a third party to keep discussions moving and both parties focused on the issue at hand.
If the parents can reach agreement about care arrangements for the child, they can have the agreement written up as a parenting plan. Parenting plans are not legally binding, which means the court is unable to act should one or both parents contravene the parenting plan, but the parents may also opt to have their parenting plan made into consent orders by the court, which will make it legally binding.
If the parents are unable to reach agreement, however, they can file an initiating application with the court in pursuit of parenting orders.
If the court is asked to decide on care arrangements for the child, it will make its decision based on the child's best interests. The pathway it follows for making such a decision is outlined in section
60CC of the Family Law Act 1975 - I suggest reading this so your partner can consider acting in favour of such considerations. There are other parts and concepts that are important as well, and I'm happy to explain these, but try not to get bogged down in this as a legal issue yet. It may not even come anywhere near court.
To organise family dispute resolution, contact Legal Aid, Relationships Australia or any other service offering accredited family dispute resolution conference. They will contact the mother on your partner's behalf, which may help avoid the risk of instant hostility.
I hope this provides some guidance in the first instance.