@jespah,
That's not at all how these things tend to work.
The sister 'used to be her rock', and there is no reason the underlying character traits that supported that sort of relationship would have changed for the worse (outside of domestic abuse, where they can become repressed). Conflict doesn't often change character traits.
Do you know why her sister believes she has to constantly walk on egg shells?
As one possibility: her sister may have been hurting over many years, watching how much Neptune is hurting. She may believe (many psychologists do) that to completely heal, Neptune needs to forgive (I would say let it slide into the past), because the holding on keeps the pain fresh, and so keeps the damage ongoing. And in so believing, her sister may have tried over and over again to 'help' Neptune forgive, in the hope of her healing...only for Neptune to react to 'her not understanding my pain'...
...or that may not have been it at all. There are many variations on the motivations in such situations.
What is fairly normal for both sides of such a situation, where emotions can be felt intensely, is for one or both parties (usually both) to communicate in ways they don't even realise are damaging...hence why mediators are so good in such circumstances.
By the way Neptune, whatever you decide, I do hope it works out for you.
