Your “pulled muscle” in your neck that you suffered with for years most likely was an annular tear or small herniation of one of the discs. Many individuals report annular tear symptoms to feel like a “pulled muscle”. Most likely, the intense pain you experienced starting 8 days ago was a complete herniation compressing the nerve root.
The muscle strength deficit is again, most likely from nerve compression. Your physician apparently performed a skilled motor examination and found the strength deficit. One hand should not be significantly weaker than the other normally.
I cannot comment on your sister and why she is the way she is currently but most likely, your life will not follow hers if you treat this condition appropriately.
Follow your physician’s advice. You should have an MRI of your cervical spine. You may be a candidate for physical therapy and an epidural steroid injection or you may need surgery. The treatment decision depends upon your examination and the findings on the MRI.
Most people with this condition and appropriate treatment have significant or complete resolution of their symptoms.