Why are DP and his sister discussing me when DBIL is dying

As mentioned on a previous thread DP suffers with anxiety and depression and after a few days of not speaking had a,spectacular meltdown. My BIL who I really like, is terminally ill and may die in the next week. DP speaks to his sister every day on face time ,at the moment ,and usually I am around to hear how BIL is.
On Wednesday our son was off college and wanted to visit his uncle . I rang DP' s sister to check if it was ok as they live 35 miles away . I also said I was checking how BIL was as I had been out the previous evening and DP had not updated me. I made no mention of the fact DP had barely spoken to me all week.
This evening DP said his sister had said I told her he never updated me on BIL' s condition. I obviously denied this,as it was not true.
DP called his sister this evening while I was out walking the dog and brought up the issue again. He told her he might have got her into trouble as he told me what she said! Apparently ,according to DP, she insists I did say this ? My BIL' s condition has deteriorated and he may be admitted to the hospice tomorrow so why is DP wasting time discussing such an unimportant issue.
I have always got on well with DP' s sister and I am trying to be supportive as I have been with a few close relatives in final days but I am now cautious about what to say. I do appreciate she is under a lot of pressure and it's a difficult time.
Hope this makes sense.