I'm not sure if this is ISFP behavior or not, though it's not healthy regardless of personality type. I will say that there are people in this world who have a hard time forgiving, and even worse they NEVER forget. Your sister may very well fit that mold. You apologized, but she may not have accepted it. She may
not WANT to let it go. She may want to use it to get back at you. In which case, it's better for you two to not be around one another. Her not being able to get over something you said isn't your fault, but you did help her get there.
Perhaps you can email her and inform her of the way she criticizes you. Tell her how it makes you feel, and that it's her attitude toward you that strains your relationship further. She will have two choices; stop behaving in this manner, or not. It's up to her. Just let her know that as long as she continues, you probably won't be spending much time with her. It would be good if she was up front with you about why she treats you the way she does, but if she really is an ISFP, that may be unlikely.
If she's fine with treating you badly, there will be consequences. It's time she realized this. She's not a kid anymore. Similarly, if she is
that hurt over past slights, well now you know the consequences of not holding your tongue.
It sounds like a sad situation. I would just let her know how you feel, and do what YOU have to do to keep yourself in good company.
Best of luck.
She's often the one to initiate these right vs. wrong battles these days..
There are many ways she looks down on me or at the very least..acts like she looks down on me.
I can't have a pleasant conversation with her most of the time since she jumps on something I say or do pretty quickly. She is very curt with me.
She has a good memory though and could very much hold grudges over things I did when we were younger. We've had our own fair share of fights. I've said some pretty mean things in the past which I'm sure I already apologized for but still..
I guess the best thing I can do is to make sure I'm not doing that on my side and be careful.
Thanks for the advice!