How to know if your chick has lethal dwarfism?

[Opiumbrella]

I had a black bantam hatch out one lone chick, it was the cutest tiniest baby I had ever seen. The chick has grown SO slow, but is not failing to thrive. Just extremely mini. She eats and runs around and flies up to the high bantam roost my bantams love, (and oddly sleeps under her dad lol not her mom) but with her age and size I'm fearng she will spontaneously die soon. She was born at the end of June. And she is not even half the size of her mother, an already tiny black bantam hen.
Is there anyway I can't tell for sure if she has fatal dwarfism?

 

[casportpony]

How is your chick doing?

 

[Opiumbrella]

How is your chick doing?

She is doing amazing. She is between 10-12 weeks old and the size of a pear lol. She is still super clingy to her mother because she is just so small compared to everyone else. But otherwise she is doing great. As small as she is, she has grown. I had never seen a chick so tiny. She was less than 2 inches high at hatch.
She has all her adult feathers, she eats good, and loves to explore (I take her out with her mom sometimes supervised when I'm working outside. And lock the cats in the house as with her size and loud cry I'm terrified my cats who normally pay no attention to the chickens will be drawn to her) she runs around digging dusting eating bugs and jumping on things lol. I'm working on building a safety run for her out where my chickens free range in the pasture, so she can safely be outside and not forced to stay in the coop all the time.
She seems completely proportionate. Just a perfect miniature copy of her mother. So im hoping that she is just fine. Thank you for asking about her.