In the UK,Australia and NZ the word "partner" has become the default term to describe one with whom you live as a couple.It's all very new-age and PC.The words "husband" and "wife" are rarely,if ever,used in these countries.
So,IMO,it's by no means certain that she wasn't married to her "partner".
That's a good point which had not occurred to me. I appreciate your pointing it out.
It makes you think that she was married in that the article refers to her other children from her first marriage. I would take that to mean that there was a second marriage--although who knows if this partner was number 2.