my daughter has received DLD diagnosis and I have been told she has been masking her Autism

My daughter is 13 years old, she has never been any trouble in or out of school, this all changed when she started high school 2 years ago, 

her behaviour is risky dangerous , she is self harming, previous solvent abuse, runs away, 

She has had 2 educational psychologist reports - both confirming her language and understanding level is between age 5 / 7 years - she's 14 next month.

She has had a diagnosis of DLD within the last month, has not been to school sine april 2022

I have been told that she is also Autistic and to get her assessed -  she has been masking for so long - professionals have advised me.

sensory overload,

does not sleep, cant drop off, be awake 48 hours and then she will just drop and sleep.

Her brother is ASD and I can not believe I have missed this in her.

Now we are aware I can see all the signs as she is no longer masking, but its like she has gone back to being a 5 year old.

anyone been through or going through the same, I am struggling to understand the DLD - development language disorder