JudithButlerNot: ‘… for example a girl may well feel like a boy, that can be something you agree on …’
This is not something you should agree on, or even pretend to agree on, particularly as it is not true.
There just is no such thing as feeling like a boy. And this ‘no such thing’ is particularly strong: ‘to feel like a boy’ looks like it makes sense, just as ‘to go east from the north pole’ looks like it makes sense. But when you look at it and think about it, its meaning evaporates.
‘I feel like a boy’ makes no sense because there is nothing that it is to feel like a boy, just the same as there is nothing that it is to point eastwards from the north pole. (Or, a famous example, the time it is on the sun …)
JudithButlerNot: ‘… its possible to be curious what that means to them .’ Again, this is mistaken. Be curious about what they think it means to them, by all means. This is to the point as there is no such thing as ‘what that means’ to them, even though they think there is.
Of course this is nuance, JudithButlerNot: we surely agree on the basics here. But it seems important to keep a grasp on how things actually are. I agree with you ‘The first thing is to find out …,’ but I would say, ‘The first thing is to find out what they think they mean.’
-- After all, the best outcome all round would be if the young person in question were to recognise the status of ‘I feel like a boy’ as what it is, prior to engaging therapeutically with whatever it was that made them try to assert such a thing. Ime young people can be helped to understand this, even if sometimes, as you say, it can be difficult for the immature mind to grasp.