In some ways, Bella does a lot, very quickly; and in other ways she does almost nothing at all.
She does not have to be secretive - she has no enemies, her world is accustomed to the introduction of strange wonders and will not fall apart with any revelation. She revives a large number of dead people - although none of Marianne's direct ancestors - and sends them home to surprised but happy families. She renders a larger number of people torchable. She sends letters to the monarchs of neighboring realms indicating that she is available to help with any unusual difficulties in which they may find themselves, and that she would appreciate introductions to their farther-flung neighbors. That is the "a lot".
But her world is made of cotton candy, and she has no intention of dumping a bucket of water on it in the hopes of rinsing off small amounts of dust. She is not usurping her mother-in-law, she is not conquering miscellaneous other kingdoms, she is not ridding the world of all its annoying but ultimately not mean pitfalls and hazards. (She does make it a condition of rendering dragons torchable that they must not eat anyone except trespassing Orthodox wizards.) She is mostly staying at home with her wives and her daughters, reading Rose's books, chattering endlessly with Kanim about all the exciting experiments they'll conduct with the new forms of magic available.
When Jane goes down, Bella has to make sheepish announcements that her resurrection powers turned out to be impermanent; she hopes they will return but can offer no timetable.
Meanwhile, news of one specific resurrection (Howard's) has spread far and wide.