Parents tourist visa - TB test

Hi all, I have a unique situation and I'm hoping I could get some help.

My parents have an existing tourist visa valid till the end of the year with a max stay of 3 months.
With twins on the way, we applied for a new visa as we wanted them to stay longer than 3 months.
Unfortunately during the medical, they found a TB like symptom for my mum and asked to undergo sputum for AFB Smear and Sputum for TB Culture. This was in April and we'd been advised to wait till July for a second x ray.
Meanwhile my mum did a private test and found it to be negative so we know she's fine.
Now back here, my wife delivered the twins pre term and now I'm freaking out as we have no support here (the babies will be in the hospital for a few weeks so it's ok right now).

Now my question is, can we withdraw the application for my mum and get her here on her current visa or do you think this medical issue is already on her record? I don't want a situation where she's denied entry to Australia. I'm happy for her to be here for 3 months as we need her now.
My dad meanwhile got the long term visa.