Hello, I would be happy to help.
In answer to your question, this is not a typical symptom of pregnancy
. Assuming that she has had an otherwise uncomplicated pregnancy up until this point, then it is probably of low concern.
That being said, I would bring this up to her OB/GYN at her next visit - perhaps you should attend that visit so that you can describe what you are seeing. It is probably just an essential tremor
, just like you suspect.
I hope this helps and good luck!