Simply put; it's none of their business and here in Australia your manager and coworkers' attitude might even be considered bullying and harassment towards you
- you just can't go around discussing people's personal lives in our workplaces, you have to tread very carefully. Quite frankly, your manager handled it badly, she should be more concerned about gossips in the workplace affecting the workplace culture, than your personal life.
If this happens again, I would be requesting advice from HR.
The above posts have summed it up nicely so there's nothing else I can add except to say that I'm a good 15 years older than you and if I saw my husband at my workplace I would be chatty and friendly with him, and if he was ill I would be affectionate with him. End of story.
You handled things really well so I'm not sure that there's anything else you can do except to try to rise above it, which you clearly are. :heartbeat I guess if you want to feel comfortable in your workplace, you might need to be careful with interacting with your boyfriend if he's at a medical appointment, but quite frankly if it was me, I would be setting some limits with your co-workers.