In the article she suggests that she 'just offered to pray for them', but then also mentions that she gave 'testimony of miracles' as well, so obviously she did actually say more than just 'I'll pray for you'.
So it is very hard to know how much she said, and obviously someone writing in the Telegraph has an agenda to push the particular version of the story that fits their agenda (i.e. woman is sacked for her beliefs).
Now, there are some evangelicals who will do things like push themselves on people with cancer, saying that if you believe you'd get better (a miracle would happen). Which kind of has an implicit meaning that the cancer is something to do with not believing in god, a punishment or something.
I imagine the truth was somewhere in between the extremes, but she said enough to offend them, otherwise she'd not have got the sack over it.
Joe