Bridging Visa B refusal - Travelling in mid Dec - Please advise

My mother's Tourist visa (600) is under processing. She is on Bridging Visa A.
We are going to India in mid December. I applied for Bridging Visa B so that she can leave Australia in December and re-enter in Australia.
However, the Bridging Visa B has been refused. The processing officer was not satisfied the applicant (mom) meets the requirements of subclause 020.212 (2). The processing officer (immigration) was not satisfied the applicant has substantial reasons for wanting to travel. I had mentioned "to meet family and friends in India" as reason for travelling to India and re-entry to Australia. The processing officer was not satisfied the reasons for travel were substantial nor of a genuine need for the applicant. As the applicant is a temporary resident only, they are able to depart at any time. Therefore, the processing officer is not satisfied the applicant meets the criteria specified in Regulation 020.212(2)(d) The processing officer have also assessed the applicant's situation against subclauses 020.212(3), (4) and (5)
The processing officer found subclause 020.212(3) is not met because the applicant or the Minister for Home Affairs have not sought judicial review of a refused substantive visa application decision within the statutory times frames.
I find subclauses 020.212(4) and (5) are not met because the applicant has not made a valid application for a Partner (Migrant) (Class BC) visa. The officer was not satisfied clause 020.221 was not met by the applicant. Based on the above stated reasons, Bridging visa B was refused

Can you please guide how should I proceed as we are planning to fly to India on 17th December:
1) Should I reapply for Bridging Visa B? This time I provide more reasons for visiting India (such as maintenance of our ancestral home, meet a sick and bedridden relative, medical check up in India)
Do I have to also give the reason as to why she has to re-enter Australia?
2) Currently, we are travelling from mid December to Jan end. I will put the same travel dates in the Bridging visa B. However, if mom was to extend her stay in India then what is the next step?
Does the immigration department give bridging visa only for the travel dates (mid Dec to Jan end in my mom's case) provided by applicant or is it for longer duration (e.g. 3months)
I read on the site that if mom miss the expiry date of Bridging visa then she will need a new visa to enter Australia

To set your expectations here, I don't think any of the folks here that contribute on the forum often are experts on Australian visa policy. I'll throw in a few questions for you to think about, but I completely lack understanding of immigration rules, so treat it with caution.

The obvious question is why can't your mother return to India and wait until her vids processing is over? It's a tourist visa anyway, so she doesn't have any work/etc that holds her there. Why wouldn't she be able to return as a tourist later when it's been approved?
I would assume the same concerns were raised by the Australian immigration department.

Some of your questions have answers on the website itself:
https://immi.homeaffairs.gov.au/enterin ... dging-visa

Your visa grant notice will clearly define the travel period of your BVB if we grant it.

We can't change or extend the BVB travel period after we grant it.

Thanks so much for the response:)
I want to email the immigration department. Is there an email address to contact immigration department. I have submitted onshore visa 600 for parent. The medical exam is on 5th December. I am hoping that immigration grant visa until 17th Dec. Does anyone know email address to contact immigration.
I had previously submitted bridging visa B application. which was refused as the officer did not find the reasons substantial and genuine. Worst case if visa does not come. Should I apply for Bridging Visa B again?

Thanks so much for the response:)
I want to email the immigration department. Is there an email address to contact immigration department. I have submitted onshore visa 600 for parent. The medical exam is on 5th December. I am hoping that immigration grant visa until 17th Dec. Does anyone know email address to contact immigration.
I had previously submitted bridging visa B application. which was refused as the officer did not find the reasons substantial and genuine. Worst case if visa does not come. Should I apply for Bridging Visa B again?