Visa for family

Hi @pinkhope.
Sorry to hear about your diagnosis. Similarly to the previous comment, I'm not sure where your sister is coming from so it's hard to offer advice.
My situation was slightly different as I was diagnosed during the travel ban so there were a lot of hoops to jump through but we managed to get my Mum (from the UK) a visa/exemption pretty swiftly to come out and support me. 
I did supply a lot of medical information to expedite the process and she had to prove she could support herself (financially) for the length of her visa. She also managed to extend her visa whilst in Australia with no issues. I think my dad initially fought quite hard from their end though with lots of calls to immigration to try and get things done ASAP. 
But as I say, depending on visa type, what country your sister is coming from, it could be a completely different story. I would say to have some medical documents ready in case you need them (getting doctors to write letters fast was quite difficult... some are on their own time!)  I sent a list of my appointments, my proposed treatment plan and a letter from my MDT saying I'd benefit from the support of a family member. 
Good luck and I hope she manages to get here soon to help you along the way. x

I understand that you're both keen to get this visa as soon as possible, but without knowing where she's coming from, I can't offer any actual advise. From the Australian side of things, I would imagine that they have a process for visitors' visas whereby they are satisfied that she will be a genuine visitor and is not trying to come in under the radar to work or stay illegally. That process probably has a set time frame. If you're anticipating a delay from her country of domicile, then she would have to prod the officials from her end. I would be cautious that any letters from you or your doctors might backfire, in as much as they might have reservations that she might try to extend or overstay her visa in order to care for you if your condition isn't stable by the end of her allotted visa stay time limit. Good luck with your treatment and your sister and her visa.