Boss Disclosed Medical Info To Coworkers

Hey, so I was at a rather large work meeting (40-50 employees) and while we were on a 15 min break one of my upper management came up to me while I was sitting at a table of about 5 other employees (we have random seatting) and asked how my procedure went (I've been having some health issues I disclosed to my manager who told this person). I was caught off guard and said I don't have results and she said I guess I shouldn't have asked and then said I hope you get some answers soon and proceed to ask me more questions about it. She knew I didn't want people to know as I had been working from home the previous week while wearing a heart monitor for 24 hours which she approved. The more I think about it the more upset I am that she asked me about it in a public situation but I don't know if she actually did anything wrong and what I can do about it. Also I'm a unionized employee and she is not. Any help would be much appreciated.