If you knew she had given you her private information in confidence and you decided to tell someone anyway, you betrayed a confidence. If there was no understanding, but you had reason to believe that passing on the information might harm her reputation in some way without any objective need to do so, you committed the offense of detraction.
Why did you have any need to talk about her surgery at all, or to disclose more than you knew she wanted you to pass on? Seriously ask yourself: what good were you hoping to accomplish? Has someone given you jurisdiction to even have an opinion about other people’s spending habits or to make yourself into their religious superiors? When you read the lives of the saints, do they go around correcting people they have no office to correct? No, they don’t. That is because they know that those who have the office to correct will be held to a higher standard. Even when they have to bear that kind of office because of their place in their religious communities, they are too wise to go looking for that job!
One of the first things to learn if you want to be a contemplative is how to mind your own business. Nothing is more suspicious, in a man who seems holy, than an impatient desire to reform other men. A serious obstacle to recollection is the mania for directing those you have not been appointed to direct, reforming those you have not been asked to reform, correcting those over whom you have no jurisdiction. How can you do these things and keep your mind at rest? Renounce this futile concern with other men’s affairs! Pay as little attention as you can to the faults of other people, and none at all to their natural defects and eccentricities. --Thomas Merton
You have described instances of people being obnoxious and realizing they’re being obnoxious, not to mention being cruel and realizing they are being cruel, but excusing all of this because they’re “telling the truth.” It is right to not let them try to sugarcoat that with some nonsense rationalizations that imply that some people are just too sensitive.
When someone asks for your honest opinion, do not use that as an excuse to abandon kindness or to excuse callousness towards the feelings of others. Ask yourself whether or not the opinion you are offering is going to do any harm or not. Not whether it is harm they can “get over” but just whether or not you’re giving them something to “get over” at all, whether you are putting an obstacle to trusting you when they are hurt and in need.
If you want to be able to extend charity–and if you are in the habit of receiving Holy Communion, of course you would be–then you must act in a way that teaches people you are a safe person to approach when someone is in need of charity.
Ask if you can put your name in for the word “love” in St. Paul’s description of the most excellent way:
Love is patient, love is kind. It is not jealous, is not pompous, it is not inflated, it is not rude, it does not seek its own interests, it is not quick-tempered, it does not brood over injury, it does not rejoice over wrongdoing but rejoices with the truth. It bears all things, believes all things, hopes all things, endures all things. 1 Cor 13:4-7
You are right, then: If you can’t say something charitable, then do not let anyone induce you to say anything at all. Learn to listen with the ears of others and taste how what you are saying is going to sound to the ears that will be eating it up. You’ll do OK. It is the work of a lifetime, especially in our days of so many words and so much talking, but erring in the direction of charity is the right direction.