I strongly doubt it was a suicide. The Australian police force were on the side of her killers, so they called it a "suicide" because they didn't want to investigate her murder.
I've read a news article about the incident, and there was no mention of the doctor leaving behind any notes. Based on what I had read, it seemed suspicious.
In the USA, it's now public knowledge that some police officers carry extra guns known as "drop guns" that they can plant on the bodies of people they kill so that they can plausibly claim self defense. (I'm not saying it happens every day, but it is a "thing".) If cops can falsely claim self defense, it stands to reason that they might also falsely claim suicide.
There is a lot of justifiable suspicion about the death of Sandra Bland while in police custody. The police department's coroner ruled it a "suicide", but her own family has disputed that. And it seems odd that a woman would end it all as a result of facing just a short time in jail on trumped-up charges.
I don't claim to be certain of the facts in either the Sandra Bland incident or the Austrian doctor incident. There are some dishonest police officers in every country, and I personally think that both of those cases appear suspicious based on the limited information I saw about them.
I strongly doubt it was a suicide. The Australian police force were on the side of her killers, so they called it a "suicide" because they didn't want to investigate her murder.