She's deaf in the comics. It was accurate to the character. As to why the Celestials would make one deaf- maybe they worried about sonic attacks, so they designed one who that wouldn't bother.
I had a problem with the Deviants. Okay, so a few were frozen, and global warming thawed them out. I can buy that. But what I don't get- and what was never explained- was why one Deviant could suddenly siphon powers and memories from Eternals. This was a trick that Ikarus said they had never seen before. So why was this one able to do it? Also- what exactly was it's plan? I get killing the Eternals for killing the rest of its kind- but the big ass Celestial about to burst from the planet would have killed him as well. Why not have Kro (was he even named in the movie?) come to the Eternals and tell them about the Emergence, and team with them to stop it- and then try to kill them once that happened. As it was, they were just underwhelming.