Family member playing mind games - do you step in?

I think I’d stay out of it. Be neutral. Stay friendly with both and provide a listening ear, but don’t offer advice unless asked. Your sister needs time to grow up and away from what annoys her.. Your mom needs non-judgmental sympathy.

If you really don’t want to just stay out of it (which I can understand), I’d start with trying to talk to your sister about things. Try to remain nonjudgemental while talking with her. If she doesn’t want to talk about it, just let her know that if she changes her mind, you’re willing to listen.

As hard as the time of your illness was on you, try to remember that it was as hard for your sister, just in a very different way. The range of emotions she felt about you being so sick was probably very difficult for her to process. She may have resented you at times for taking up so much attention from your parents, then felt guilty because she knew it was necessary. She may have resented your parents for having to spend so much time and energy on you, but felt bad because she recognized that there were no other options. She may finally have decided, unconsciously, to focus her hurt and anger on your mother, because, well, she’s the mom. I’m not saying she’s wiggy, but an ill sibling is hugely difficult for a well one to process. Counseling can help if she’s open to it. This kind of family dynamic can be enormously stressful and disruptive, and because no one is at fault, it makes it harder.

I would interfere, but in the way @Seaofclouds said. I would talk to the sister about why she feels disconnected from her mother. That needs to be brought out into the open before the two of them can really speak.

Maybe she feels like your mom pushed her out of the nest before she was ready…...?

Could it be your health conditions that are playing a big part in this resentment? Your mother is apparently spending a lot of time with you, for this reason, and maybe your sister is jealous and inadvertenly taking out her jealousy on your mother, instead of you? Is this possible?

There has to be a reason your sister is acting this way. The heavy burden is on your mother, if you know what I mean.

I know you love your mother and maybe you should have a serious sister to sister talk and discover what her problems are. Apparently, your mother cannot do this, so it’s up to you to play detective and get to the truth.

Its time for you to return the favor to your mother for all the attention she has been giving you. Come to her aid and give your mother some relief.

You know what I mean? jp

I’d stay out of it but encourage your mom to talk directly with your sister about how they can better communicate or at least agree to disagree on a few things and leave those things alone.

To me, it sounds like your sister is jealous of you. You seem to have a much closer relationship with your mother than she does. Also, your Mom “walking on eggshells” around your sister seems like a really bad idea. If she is doing that, she is probably also treating your sister like she does not trust her. I don’t see how that is healthy. It sounds like she needs to start treating your sister like a daughter instead of an acquaintance she doesn’t quite trust for some reason or other.

@AnonymousGirl : There’s a rather extensive backstory that the OP hasn’t gone into in the details.

Okay.