Wow, one afternoon a fortnight? Mate, you need to give yourself some credit - your daughter needs you more than one afternoon a fortnight, especially at an age when she is developing attachments to her parents.
Under s60B of the Family Law Act 1975, children - not parents - have a legal right, which is to know, spend time and communicate with both parents on a regular basis, regardless of the status of relationship between said parents, and it is the court's duty to ensure your child's rights are upheld, insofar as their best interests are met. All parenting orders made by the court must reflect the child's best interests, and you can read s 60CC of the Family Law Act to see what the court considers when determining what's best for the child (though court is still a long way off for you).
There is a presumption under family law that both parents have equal shared parental responsibility for their children, which means you have equal say about major long-term decisions related to the child, including care arrangements about who she lives with and when she spends time with the other parent. Equal shared parental responsibility cannot be removed unless by order of the court, and it is not a common outcome for the court to make that order.
Where shared parental responsibility is upheld by the court, the court must consider whether it is appropriate for the child to spend equal time with each parent. As well as considering if it's in the child's best interests to spend equal time with each parent, the court will also consider if it's practical (if the parties live too far apart, their employment rosters make it impossible, they are unable to communicate, etc.). Realistically, I can't agree it would be best for a child of 7 months to spend equal time with each parent because of the age, but as the child gets older - say when they start school - equal time arrangements might be more workable.
However, if the court were to decide it's not in the child's best interests to spend equal time, the court must then consider if it is appropriate for the child to spend substantial and significant time with each parent. Substantial and significant time is a mixture of weekends, weekdays, holidays and special occasions, such as alternate weekends, one night each week, birthdays, Father's Day, Christmas, Easter, and half school holidays. Again, an order of this effect will only be made if it's in the child's best interests.
So, basically, what I'm saying is that your child has a right to have a relationship with you, and provided it's in the child's best interests to continue having a meaningful relationship with you (that is, you're not a risk to the child's welfare), then you should be aiming for more than one afternoon a fortnight, if not only because it would be impossible for a young child to maintain a meaningful relationship with a parent who they see so little.
But you're a very long way away from court, yet. Your first step is to contact Legal Aid or Relationships Australia to organise a family dispute resolution conference with the mother, which is where both parties meet under the guidance of a third party to try and reach agreement about care arrangements for the child. If agreement can't be reached or one party refuses to attend, the mediator will issue a s60I certificate, which enables you to file an initiating application for parenting orders with the court. Mediation is a mandatory pre-procedure step, so it cannot be avoided except in some circumstances (e.g. where there has been family violence, etc.).
The court frowns on parents who refuse to facilitate time between parent and child because it's shows they are unsupportive of the child's relationship with the other parent and lack insight to the child's emotional needs. With any luck, the mother will attain legal advice informing her of this and it might prompt her to reach agreement about the child spending time with you, thus helping you both avoid court.
Remembering that I don't know the other party's story, and that this isn't legal advice, I hope this is in some way helps.
