I was in a similar situation where I earned more then the rest of my family.
I had a rocky relationship with my sister but constantly helped her with money, my DP pointed out one day that it was the only reason my sister ever bothered with me.
I lent her a big sum then tried to spend time with her but she just brushed me off, my eyes were opened and I realised how transactional our relationship was and it really upset me because she was my only living family member.
I cut contact completely and I see it that the money was well spent to have the realisation that I was nothing more than an ATM. It still hurts and we got back briefly in contact but due to her now prioritising a man over her own kids the relationship has deteriorated again.
What I will tell you is that you did a really good thing.
After years of bulimia I was going to lose my teeth and was devastated, I was at rock bottom and no one could help me with the money, I was in a dark place as I had such low self esteem that it made me contemplate suicide.
In the end my employers helped me with the money as they knew how desperate I was. It was a lot of years ago now but I’m still so grateful, I have never taken my teeth for granted again and it helped me recover from a 20 year eating disorder.
Your sister is probably jealous and maybe doesn’t see the gift you’ve given her yet, maybe she does but just can’t show it because of the overriding jealousy.
She will appreciate it and you did an incredibly good thing, you will have made a huge difference to her life and I hope this makes you feel a bit better. I’m sure you still care and it’s important to you that you changed your sister’s life whether she shows gratitude or not.
I’ve learned the hard way that money doesn’t change people or build bonds, if someone genuinely isn’t bothered about you then they might fake it for money but they can’t sustain it. Draw a line under it and think that you have helped but don’t have to keep on giving to people who will only take and never give you anything in return.
You sound like a lovely caring person and I know how much it hurts when family just want you for material reasons. Spend you money on yourself and put yourself first, please don’t give into any guilt trips and see what happens when you stop being a cash cow.