Please talk to me about Bipolar diagnosis

[Dollymaid]

My DSD has been diagnosed. I have total regard for MH and often support staff through my work....however and I am so worried about being seen to be uncaring and not understanding, why do I not feel convinced about this diagnosis?
I want to understand more; want to support but feel that the little I know about bipolar, combined with what I do know about my DSD just doesn't add up.
Is a diagnosis always reliable? How is this made? I have read information about bipolar and a diagnosis but this suggests a series of questions to be answered, there must be more to it than that.
Really do want to help, but need to understand more.

A diagnosis is an opinion of experts who weigh up what they see and what best fits, it can (not always) determine treatment. But it can also be wrong (and there is plenty of anti psychiatry groups out there) but there may be stuff that they know that your DSD has chosen not to share with you. Specifically for bipolar you only need to have had one episode of mania (as well as depression) to meet the criteria.

Personally, rather than get into a battle about how “truthful” a diagnosis is I would look at the symptoms/distress experienced and see how you can support to manage those and improve quality of life.

Yes, I do realize that I don't have the expertise. I see a girl who is destructive and demanding. This is a child that I only know as an early 20 year old. A girl who demands, who spends, who is reckless, signs of addiction intermittently. I want to understand what is part of being bipolar and what isn't. At the moment it feels she is using the diagnosis as a justification for her behaviour, she says 'see I can't help it'.

I just don't understand and need to.