My 6 yo DD has suddenly developed.....

[SpookyMadMummy]

An imaginary friend
And her friend is naughty

She also has ASD.

How do I deal with this? Do I reinforce to her not to listen to her 'friend'? or ignore it completely?
Any advice gratefully received.

imaginery friends are okay, and in my experience they are generally more wicked than DCs, i think this gives them an outlet to be naughty

I wouldn't worry too much about it. She is probably using the friend as a way of testing out boundaries. Or maybe she is lonely and is trying to make some company for herself.

If the 'friend' does something naughty, you should explain to DD that it is not acceptable to do that. But I would not completely ignore the friend, and certainly would not tell DD that the friend does not exist. As it happens, the friend does exist - in her imagination.

You will probably find that it passes in time,

Thanks. Its hard enough with her at times without the imaginary friend!!
Not mentioned her friend today so far, so with a bit of luck she has forgotten already!!