Your friend should see a succession solicitor ASAP.
the laws are slightly different in each state, but in a nutshell, she would have standing to make a family provision application as a child.
The potential for success will depend on your friend's financial situation and need, the value of the estate, the financial situation and need of the brother. Estrangement is not fatal to a claim, particularly if the parent instigated it.
there are strict time limits for claiming. they vary depending on the state. For example, the time limit in Queensland is 9 months to file a claim, but the executor can distribute without being personally liable after 6 months, so you have to make sure you give notice before 6 months and then file before 9 months.
In Queensland, at least, there are good dispute resolution procedures in place for family provision applications, meaning the majority of claims are settled without actually having the expense of a trial.
there are also solicitors who will take family provision applications on a "no win, no fee" basis, if they think the claim has merit, so not being able to afford to pay the legal fees up front is not necessarily a barrier.
(i have only read the first post)