Dianne Feinstein is well aware that if she were to resign that it would put an end to Dems ability to confirm federal judges as Repubs could and would block appointment of her replacement to the Senate Judiciary Committee.
https://time.com/6281088/dianne-fein...supreme-court/
Quoted from the Time article linked to above:
"Even if Feinstein were to leave her seat early, allowing California Gov. Gavin Newsom to appoint an interim lawmaker until after the 2024 election, there is nothing ensuring that that successor could be the 11th vote on Judiciary. Committee assignments are part of the start of every Congress, and changes are subject to 60 votes if some lawmakers object and demand a recorded vote."