No not really "built in" or "in built" is only used for buildings or machines etc.
To be jealous is a characteristic of herS.
You pluralise her in that sentence to make it similar to the 's possessive comma of ownership.
It is typical of her to be jealous.
To be jealous is a characteristic of herS.
It is typical of her to be jealous.
You could ask another question why is there an S on first sentence and not on the second sentence.
I have completely forgotten, it being a long time since I have been in an academic environment.