I haven't experienced this at work but I did whilst in the hospital. I've had melanoma before & it returned Stage 3 several years later. Whilst in hospital, recovering from the groin/pelvic dissection, a young female on the ward was going onto the car park 'scoring' heroin & then taking it in the toilet. Her behaviour was erratic but the nurses could only keep an eye on her. She overheard a conversation between myself & another patient & realised we were both Police officers. Later that day, after the other patient was discharged, she started ranting & raving at me, saying how she was going to get me for telling on her to the nurses (which I hadn't done)! Up to that point I thought I was dealing with my diagnosis quite well but I dissolved in tears (the first & only time until then). What upset me was that, after 30 years in the Police I had never let anyone get to me mentally, but while I was vulnerable this female had reduced me to tears. Fortunately another patient alerted the staff who moved the female & the sister sat with me & made sure I was OK. 

So, it doesn't matter how well you perceive you are doing, if someone says or does the wrong thing at the wrong time it knocks you for six. Don't beat yourself up about it, be kind to yourself, accept that you are, like everyone in these circumstances, still vulnerable. It takes time to build up the mental strength to face this type of behaviour but you will get there. Don't let one lunatic person knock the stuffing out of you. Accept how you feel, gather your strength & take your time to get back on your feet. Meanwhile, I hope your management are aware of the incident & are ensuiring that she has been dealt with for her inappropriate behaviour.