Hi,
It is very unfortunate that your neighbor shared with you information that was not to be given out. I agree you should pray for your neighbor who has cancer and also pray for the neighbor who told you. She broke confidentiality and if the one who has cancer finds out she may not ever trust her again.
With all that said, it is obvious from appearance sake something is wrong with your neighbor. I had the same surgery almost 2 yrs. ago and wore hats.
Hope your neighbor eventually shares with you, but until she does, just pray for her.
God Bless you,
Bev