Getting Re Diagnosed

Is it possible to to get a re-diagnosis form the Adult services.

I've 2 Children (Adults ) on the spectrum and my first was diagnosed at 23years old by adult services and was a clear and thorough diagnosis and all the Psychology speec & language assesments, thorough and conclusive at a Level 2 Autism.

My 2nd child i had to Push hard with Camhs (because she's a female) and it wasn't until she was almost 18 they agreed an ADOS (level 4) and alongside a private 2nd opinion who looked into the background of how Camhs had diagnosed her with everything but ASD, it was very rushed and whilst they diagnosed ASD they've just kind of left it there and discharged with no further referals owing to her being 18 at diagnosis. 

I'm now left with this backlash of going forward only to be left not knowing at what level ASD she is at, or where she goes from here.

it so messed up that i'm thinking maybe she needs to start again through Adult services and get rediagnosed, is this something or not?