Why not 'Zij is precies even mooi als haar moeder'?
It's either "precies zo mooi" or "even mooi". :)
How does one know it's "mooi" and not "mooie"?
The adjective comes after the noun it is describing, so it is not modified.
het meisje is mooi
het mooie meisje
een mooi meisje
Are ‘precis’ and ‘net’ mutually exclusive?
Surely no native English speaker would say 'She is exactly as beautiful as her mother'!