Glad to see that they were able to save her.
No, she's fucked unless they pull mom right out of the picture permanently.
The girl is a minor and if the mother wants to be difficult she could cause irreparable harm with frightening speed. After the 'honeymoon period' where your pancreas is still functioning somewhat is over you are probably looking at two weeks at the high end and a maybe a few days before you would be too bed ridden to do anything to save yourself.
This of course completely ignores the far more insidious problem of simply not managing the disease well which sets the child up for problems down the road. Blindness, neuropathy, amputations, infections, injection site scar tissue (causes issues with insulin uptake -- too many bad sites and things become complicated), and a host of other fun things are the obvious physical issues. Then there are all the mental issues that somebody with support faces (stress and depression are pretty common) never mind the mental issues revolving around having your own mother essentially say "fuck you, you should be dead."
Personally, I'm inclined to cut out this woman's pancreas, hand her a glucometer and some insulin, and tell her she has to stick to her guns for about 72 hours before the choice becomes irreversible if she prohibits medical intervention.
Yes, I'm a bit of a dick.
I'm also an adult onset type 1 and know how hard this has got to be on a kid even under ideal circumstances.