I'm sure she wants you around, but maybe your reactions to the situation make her feel insecure. Her sister may be offering her the emotional stability she needs in this situation, which is why she goes to her. I think it's great that she feels safe enough with her sister to be able to go to her. Don't take it personally. I can only imagine how horrific it would be having your child going through this, and you are entitled to your feelings. Just keep in mind that whatever you are feeling, she can see it and I'm sure she doesn't want to see you hurt either.

Of course she wants you around and cares about you. Parents are usually the last people to find out about things no matter how great they are. It sucks hey? But don't feel like there's anything wrong with you because most adults I know say the same thing! My brothers always came to me. I guess because I was more on their level?

well put it like this, I have an older kinda sister. and used to go to her always for anything.  I think you should feel good that she is speaking to somebody.  Remember you are someone she really loves and holds close to her heart and she doesnt want to see you hurt ( crying ect ). And I think its a pretty big deal already for her to go for this surgery  again, I know I'll be dead scared. But I think the experience she has had from the first couple of times when she went for the surgery, I dont know how you reacted ( I can imagine , crying and just scared of what could happen). Children can feel what there parents feel, even if they are only 2 yr and 11 yrs. So  you need to be strong for her and dont push her to speak to you, She'll come to you sometime.

Just let her know that you love her, and that you here for her. I think she'd like you there, it just hurts her to see you like that. And at that moment she needs to focus on herself.  Remember she's going through alot even if she says nothing.  Good Luck