I think she will not pass a constitutional challenge. From the article:
Newsom's office told Fox News Digital that Butler moved to the suburbs near Washington, D.C., when she became EMILY's List president in 2021, and that she has a house in California. The governor's office added that Butler will re-register to vote in California before she is sworn in.
But the Constitution does not say resident, but inhabitant. She is not currently an inhabitant of CA if she is living in MD. And changing it before she is sworn in is too late. The Constitution requires her to be an inhabitant at the "time of election". I would think a decent lawyer could make the case that her time of election was when Newsome nominated her.