California Inheritance/trust Question Re Rental Income

Greetings. My wife and her sister are the sole beneficiaries and trustees of their father’s estate. He died 18 months ago. The father left two properties, one to each daughter. The one left to my wife generates rental income. To date, the daughters have dragged their feet about transferring the properties from the father’s trust to each of them. Meanwhile 18 months of rental income has gone into the father’s checking account, which remains open.

Question 1: Since the properties have not yet been transferred, to whom does this rental income belong? Did it become my wife’s property as of her father’s death date, or is it part of his trust’s property until the property is transferred to my wife’s name?

Question 2: I suspect that my SIL is dragging her feet on this because she doesn’t want to lose the rental income stream which today is going into a perceived “50/50” pot (i.e., the father’s checking account). After 18 months, I’m at my wit’s end. Is it possible to sue my SIL for breach of fiduciary duty and have a trustee appointed by a court?

Thank you.