what is proper protocol for me to extend to my sister in-law on the death of her mother

by Cal
(Naples, Fl., U.S.A.)

My sister in-law's mother just passed away. She did not contact me, but did my father and he told me.

We, she and I, are not close but not unfriendly, just busy with our own lives, but do live in the same town.

My sister in-law is only tied to my family by her daughter, my niece, as my bother died some 10+ years ago, and she remarried about 8 years ago.