Hello Annija.
Shivering and weakness can be common symptoms of unregulated diabetes and so many other conditions. Because unregulated diabetes can become life-threatening if left unmanaged, you need to seek proper medical care for her; either at your regular veterinarian or request a referral to a specialist.
With the proper care, 11 year olds can lead many more years of a good life.
Dr K
i’d get her in today, if possible JUST to make sure.