How Risky is a Open Lung Biopsy

Hi! My Mother is 63 Years old. She has been a diabetic for the last 20 years. She is currently hospitalized for renal failure & Lung infections. The Doctors despite their best efforts have not been able to diagnose the Infection in her lungs even after conducting bronchoscopy. She has trouble in breathing without aided oxygen. she is currently on steroids but they have also not been fruitful to help.
Doctors have not suggested that they have a open lung biopsy done to diagnose the infection in her lungs. As she has a renal failure, we have been told that there is fluid in her lungs as well. We are worried as we have been told she needs a ventilator support during the open lung biopsy procedure. doctors have added that this is a risky procedure as she might not be able to get off the ventilator at all.
i sincerely ask my fellow friends here to help me understand the situation better as we are in a "catch 22" situation unable to decide whether to opt for the biopsy or not.
As of now my mother is conscious, if she does not come off the ventilator support, we will be riddled with guilt for having pushed her to this condition.
please help me with your valuable suggestions.
Thanks in advance.

Anand Khanna.