en_tn/gen/16/04.md

So he went to Hagar

This is a polite way of saying that he had sexual relations with Hagar. See how you translated a similar phrase in Genesis 16:2. (See: rc://en/ta/man/jit/figs-euphemism)

she looked with contempt on her mistress

"she despised her mistress" or "she thought that she was more valuable than her mistress"

her mistress

Here this refers to Sarai. A mistress has authority over her slave. Alternate translation: "her owner" or "Sarai"