Opinions, please, on how to deal with difficult sister relationship.

Maybe you could write (I would advise against turning up at her door) once more to ask how she is doing. No mention of the difficulties between you, just let her know you are thinking of her. Then leave it up to her

For whatever reason she has gone her own way - please don't let it burden you

This is wise advice.

Are there any other family members who can shed some light on the situation?

If not, then you should acknowledge that you have done your best, and leave it at that, except maybe a get well soon card.

She knows how to contact you if she wants to, but now it's time to concentrate on your own life.

I no longer see my sibling who always made me feel bad about myself and am far happier now. No stress about an unexpected phone call to set things off again. Sounds as if yours has a similar effect. Why carry this on, if she were a friend would you want her friendship, rather think not.

Would you choose to have a friend with those characteristics if she wasn't your sister?
Normally the answer is no.
If yes, you need to find your worth and pick friends that appreciate you

There is no obligation to have relationships with people with common DNA.
There are many reasons: personality incompatibilities, you have nothing in common, different priorities, etc.

Stop chasing her and find your happiness. She is not worth it

You've tried so hard for so long DeeZ now is the time to put your own well being first.

Your sister knows how to contact you if she wants too so could have told you at the time of her diagnosis. Perhaps she feels that telling you now will make you feel guilty and that was her goal. Don't let her succeed.

You cannot change the way she treats you but you can decide whether or not you'll allow her to hurt you. Get on with your own life and leave her to get on with hers.

As biglouise has said Blood is not always thicker than water and as much as we may wish it wasn't the case, sometimes our lives are happier and healthier without certain family members in them.

Lead your own life, keep the door open (cards at birthday etc, share email address, mobile no. etc) but no more. Let her get on with her life.

I have a cool relationship with my sister who was the "golden princess" while I was the "black sheep". The only close relative who ever saw through her was my grandmother.

I chose a very different lifestyle from her (no children/travel/university/career) and I know she resented it because she had a child at 16.

I never went officially "no contact" with my sister but I did not give her my new phone number when I changed it nor does she have any of my mobiles. She does know my address and thats all.

In your position I would keep things cool and get on with your own life. Why make things needlessly complicated? Blood is not always thincker than water and we choose our friends but not our relations.

You tried your best, my suggestion would be to leave it at that.
Concentrate on enjoying your own life, best wishes .
Ps . She isn’t hurting you , you are allowing yourself to be hurt by her . You are the only one that can control that.best wishes

I have three sisters and a brother we had a difficult time with a family situation. It became so stressful and argumentative I was ill because of it. It went on for a few years until I said enough. Our relationship is now the odd card or text that suits me
and my life is better for it.
You take behaviour from family that you wouldn’t from anyone else. It can be a vicious circle that repeats itself as you make excuses for a persons behaviour. Its probably time to move on and get on with your own life.

I agree with Oopsadaisy you have done what you can to help your sister. Time to put the problems aside and get on with your life. Leave the door open for her to contact you and move on. It's sad when a sibling relationship fails like this but sometimes there is no more you can do.

I think you have done all you can, she is your sister in name only, a friend wouldn’t treat you as badly.

I can only say what I would do in these circumstances, not really knowing all of your situation.

You have reached out to her, offered support and help if needed. She has chosen to ignore it and I therefore think she really does not want you in her life. Of course, this may change in the future and you may be able to reconnect with her.

Maybe you could write (I would advise against turning up at her door) once more to ask how she is doing. No mention of the difficulties between you, just let her know you are thinking of her. Then leave it up to her.

For whatever reason she has gone her own way - please don't let it burden you.

I too have a tricky relationship with my older sister, who has always been bossy and easily offended.
Since my mum died, I have been able to distance myself to a large degree, but still keeping the door open. I had some good advice on GN which helped.
In the end, I have worked out that my sister is jealous of me, although hard to understand, it's the only emotion that fits her behaviour. I can't solve it, and it's not my fault, so I let go of any guilt. Would it help if you stood back a bit and tried a rethink?
My sister was sickly from a small baby, and got used to the attention when she was ill, consequently she relies on her health to get attention, or avoid doing things she doesn't want to.
Her behaviour was very odd when I had any illnesses. I've managed to join up the dots now but the logic is skewed.