I agree with EIQuilter. Just ask your sister. I'm sure she will be glad to let you know her feelings.
I have survived breast cancer twice, radiation, mastectomy and reconstructive surgery (most recently 5 years ago) and I have mixed feelings about having a pink ribbon quilt (I don't have one and have never made one). On one hand, during my treatments, it meant hope and support. Now, I don't want a constant reminder of what I went through. I am happy and proud to be a survivor but don't want to be thought of as a victim. I will pray for your sister's complete recovery.