I agree its a strange question, but I have discovered over the years that its a normal question treatment providers ask.. after the first time being asked this I started turning the tables on this question by telling my treatment providers a quick "no is this a trick question?"

some told me they were just curious

others told me yes it was one of their trick questions to find out how I feel about my alters ...do I think of them as friends\imaginary friends which would have ruled out my diagnosis of DID or did I think of them as a dissociation problem that happens to me and affects my life in negative ways.

others have told me this question helped the treatment provider decide the path of treatment, if a person has a favorite alter that can sometimes mean thats the alter they switch into the most and points to the most triggering\upsetting thing that everyone must deal with.

example with these treatment providers if I had said Rainy was my favorite they would have gone on the premise that depressing, sadness and storms was the main trigger in my life due to thats the alter I would switch into the most. therefore first goal in treatment would have been to work on depression, sadness and ways to make storms less triggering for me.

yes a strange question but I have learned that there are reasons why a treatment provider asks the kinds of questions they do at the moments that they ask them...

my suggestion is think about yours and the treatment providers conversation, maybe something in there will point to why your treatment provider asked you that, at the moment that it was asked and you can always ask your treatment provider why they asked that question if it still feels like a strange question to you.