Congratulations LotusLeaf on having the courage to take care of yourself by cutting Sister 1 out of your life.

How can you deal with Sister 2 being unhappy because there is disharmony between you and Sister 1?  I can only offer that you love Sister 2 and remind her that you need to love yourself first.

Plus you can love Sister 1 at a distance and if you can do that then remind Sister 2 that is what you are doing.

You can educate Sister 2 about boundaries as well.

Mark