She sumittied her application with our supporting documents are the following:
My wife's doctor letter for upcoming baby so she can help her after the babe born
This is probably the reason why your mom-in-law was refused as it is clear that she is coming to Canada to take care of your newborn child = Working illegally on a TRV
If I'm not mistaken this was the same situation when your elder child was born too i.e. your mom-in-law wanting to visit to take care of him/her = TRV refusal in 2015
IMO, your mom-in-law had a weak application which unfortunately, guaranteed TRV refusals both times. Here's why:
Affidavits cannot be enforced. Hence, they don't work for visa applications.
2) her husband death certificate
This worked against her and it explains the refusal reason for 'Family ties in Canada'. As your dad-in-law has passed away, her family ties to Pakistan are weak. And, submitting his death certificate only reiterates this point.
It would have helped if your mom-in-law needs to return to renew your dad-in-law's pension (if that's the case)
3) she took her property paper but visa center refused to take
She would need to submit the property ownership documents (legally in her name) + property valuation (either self or by a property assessor) + recent property tax receipts + support documents to reconfirm the indicative market value for the property.
All documents must be in/translated into English by a certified translator.
4) her old passport travel history
Generally, only travel to the US, UK, Schengen countries, Australia/NZ would count as travel history + she would need to prepare a Travel History explanation (visa details + entry/exit dates + purpose of each visit)
Did she borrow money shortly before she applied? Are the funds in her bank account her own or transferred from someone else? Does she have other financial investments (bank term deposits, mutual funds, shares/stocks, pension funds, jewelry as investment)?
Note:
You did not include your bank statements. So if her financial situation is not strong, it explains why she was refused for financial assets because her TRV application did not have the additional financial support from you as the host
6) bought the ticket for 2 months with returned date.
Plane tickets do not assure a TRV approval. Also, a visit of two months is too long and it explains why she was refused for 'Proposed length of visit'.
She should have kept her visit to 3-4 weeks max. + included a detailed day-by-day itinerary for sightseeing/meeting friends and family/activities with expense estimates.
7) she did write the letter that my purpose of visit to help my daughter after her baby born.
As I have explained earlier, this is the reason why she was refused twice i.e. in 2015 and recently
8) A letter from her unmarried daughters that we have strong attachment with our mother and family relating issues including our marriage in coming future as a more responsible mother after the death of our beloved father.
Again, affidavits do not work. What works is hard evidence.
As her daughters are non-dependent adults, the strength of your mom-in-law's family ties to her daughters is reduced.
It would have helped if (for example) one of her daughter's marriage was scheduled..... and if your mom-in-law had included evidence of the marriage (wedding card, bookings for venue/caterers/florist, etc, invitations mailed to guests/relatives, etc)
Here were above my mother had applied for TRV from ISB Pak but this time her application checked in Dubai office..
But I found at the end of letter there is not sign of VO officer of his/her on refusal letter
It's certain that she has been refused this time.
Other suggestions:
1. Your mom-in-law must also include 1-2 other reasons with evidence of why she must return to Pakistan by a specific date
2. Although it is not mandatory, she could purchase a refundable/date change allowed overseas travel medical insurance policy