If she sells the unit, your landlord will be the buyer.
Your rights as tenants will remain the same as they do with your current landlord.
If you have a term lease (12 months, 6 months, etc.) you can remain there until the end of that term.
If you do not have a "term lease" (12 months, 6 months, etc.), and are on some form of "month to month" lease (holdover tenancy, tenancy at will, tenancy at sufferance - these terms used to have a significance, they are now used interchangably as "month to month" tenants)., your new landlord can terminate your lease with 60 days notice.
You are entitled to the return of your security deposit just as you were before. Except now, you can hold both the new landlord and the old landlord responsible for that return (if the new landlord claims they don't have it, you can sue both of them).
For an excellent overview of landlord tenant law in California, here is a link to the California Attorney General's Landlord/Tenant handbook: http://www.dca.ca.gov/publications/landlordbook/index.shtml