I'm so sorry to have lost a close family member.
After passing through the season from the last farewell to the funeral, the first day of death, and April, I can guess that those left behind are in the process of chewing on the grief of parting ways little by little while being chased by their daily lives.
On the next 49th, when we are once again told that each and every one of us faces “life” due to the death of our grandmother, we will be able to accept that the lives we have passed away are still guiding us and working even now.
Now, let's talk about the “division of bones” you asked.
In the Jodo Shinshu sect, there is basically no division of bones, nor decisions about when to do it.
As shown by Master Wada of Chokakuji Temple, there is also a fact that they recommend dividing the bones into the head temple or mausoleum in Kyoto.
One is a wish for people to encounter Nembutsu and Buddha's teachings through the bones of deceased people.
Also, historically, the remains of Buddha have been scattered all over the world, and there is also the fact that they have been worshipped by Buddhists as Buddha reliefs.
Also, there is no fixed time for bone division. However, I think there is a reasonable reason to split the bone when everyone gets together on the 49th day.
Therefore, please consider that there is no problem with the teachings of the Jodo Shinshu sect.
By the way, the problem of “boredom” is often heard when splitting bones.
Try searching the internet for “nobotoke.”
What is explained during bone collection is actually the second cervical bone (bone at the back of the neck), and since the drop that usually moves when you inhale saliva is cartilage, it becomes ash and leaves no shape.
Since that shape looks like a Buddha meditating, it is sometimes treated as special, but in the Jodo Shinshu sect, every bone is an remains as a “link” to accept that a precious person has passed away, so there is no superiority or inferiority to bones.
If you want this degree of boning, your relatives would also like to think positively about the preciousness of saying nembutsu in connection with bones.
Yume Yume, go around your grandmother's bones and don't fight each other or cause trouble.
If you can't come to a conclusion right away, consulting with the chief priest of the temple is actually the surest path to a solution. The chief priest will also be happy to consult with you.
I'm very happy that you asked the question at hasunoha, but after all, I want all the monks to rely on the monk and chief priest closest to you.