Effects of injury on characters and character progression

The character I've been toying around with is the much younger sister of a woman whose supposed to be powerful enough to stop what's essentially Ragnarok. Older sister is nigh indestructible, invincible and all powerful by this world's metric and miles more than suited to the task, but she shows an extreme disinterest in stopping the end of the world. On the other hand, the younger sister is very driven to take on the burden of her sister and also holds considerable power but displays a drastically noticeable difference in her own abilities, being dwarfed entirely by her older sibling.

The protagonist is childhood friends with the younger sister; everything's cheery between them. Protagonist goes away for a while and tensions rise in the family about what to do about the impending doom. Young girl attempts to run away and stave off death herself, but is stopped by the sister immediately. Tears are shed, platitudes are thrown around and eventually violence ensues. Younger sister is predictably unable to put up a fight and is brutally put down.

She's hospitalized and thrown into a several months long coma. When she wakes, she escapes on the grounds that everyone was certain she would be unable to move. It's a very clumsy, feeble and reckless display.

She meets the protagonist in a far off town to continue the plot. Protagonist immediately understands that her friend was injured in some major fashion, but the young girl actively avoids explaining how she was hurt. The protagonist notes how her friend has changed from what she used to be as she seems to be much more short-tempered, has trouble processing information and is much less personally understanding than she was before the protagonist left.

/r/writers Thread