Colleague who lost her husband

Had a colleague who very tragically lost her husband at only 39 years of age. She was left with a toddler and was working in our office.

For 2 solid years, all she did was talk about her deceased husband. A 10 minute meeting would turn into a 2 hour meeting as she'd hijack it to talk about her husband. Despite efforts to turn the conversation around to work matters, she always found a way to bring it back to him. As a manager, I found it torture.

Everyone on the team, including me, was very patient and supportive of her. After 2 years she moved to another department and I have only bumped into her occasionally since she moved.

However, each and every time I bump into her and exchange pleasantries, she answers with the most horrific stories and I walk away feeling depressed. Last time I saw her and waved from a distance and she came running over to me to tell her her son had been in hospital and everything's awful etc. The time before, her friend's husband died. The time before, her mother was being awful to her. The time before, her deceased husband's parents didn't want her to talk about her husband so much and "don't appreciate that is her way of grieving". The time before that, one of her investment properties had a leak and drama, drama.

My own child spent a long time in hospital with a very serious life-threatening issue a couple of years back and she literally, in passing, once asked me how my kid was. Barely listened to me answer. My mother in law died a few weeks ago and no word of sympathy or even acknowledgment from her and yet when I bumped into her on Christmas eve, all she did was moan about her newest batch of catastrophic problems.

There's rumour she is coming back to my team in a few weeks and I'm panicking. I can't cope with her. She sucks every grain of energy from me. I appreciate life is obviously hard for her, but we all have our own issues to deal with. My life isn't exactly a park walk either but I don't drop all of my problems on her lap.

Any advice from fellow managers welcome.