Welcome to the forums
@spamvicious. Lots of virtual hugs to you, your sister and your niece at what must be a very difficult time.
As regards insulin amounts, everyone is different, so it's normal to take some time to get someone's levels under control. They also prefer not to lower levels too fast because that can cause damage. And it's usual to gradually increase the amount of insulin rather than start too high, so as to avoid hypoglycemia.
So, I think your family will probably in a very good position to ask for a pump and a continuous glucose monitor, though both have to be inserted and am not sure how well your niece will cope with that? Also, her diabetic team may want her to get used to insulin pens and glucometers first, because they are the back up when either pump or cgm fail. The sad thing is that injections are much more painful when done by someone else rather than yourself. They can also sting a bit if the insulin is straight out of the fridge, which may be the case in the hospital.
There is a parent and children subforum here, which may be useful, both the child section for your niece and the parent section for you and/or your sister.
Diabetes Forum • The Global Diabetes Community
You could have a search for autism there. There are also a number of threads about children reluctant to inject.
As regards your sister being a technophobe - it's worth using the technology now available for young T1s, though your niece may be old enough to handle it on her own if she gets past the needle phobia.
Good luck to you all.