On her gravestone, she is known as Ионас Полина Германовна, which transiliterates as Ionas Polina Germanovna [presumably after her father, Herman].

Mom's Memoirs:

He (Raphael) had two younger sisters, Pola and Fanny, both gifted pianists, Pola taught Piano as far as I remember. Pola married a Pistrak, one of two or three brothers, who spent their summers at the same resort the Jonases did. They went to live in Moscow, he was an engineer, and after the Soviet takeover in 1917, they never came back to Poland. I believe my father only saw her once more in his life.  It was impossible to go to Russia in those days so my father was only able to go there once to visit. 

...

From an email:

Well, let me refresh your memory then: my father had two sisters; the younger, Fania, married a Uryson, had no children, and she and her husband were taken to a death camp; the older sister, a classmate of my mother's, Pola ended up in Moscow at the end of WWI and married Jasha Pistrak. Pistrak was one of four brothers who my father knew since childhood, the families spent summer vacations in the same place; one of the brothers was deported to Siberia, I believe, as an anti-communist, one ended up in the States, one was the father of my friend Pavlik in Paris I don't exactly remember what happened to him, he and his family were fleeing Russia during he revolution, his wife's sister was Mrs. Alter ,"Tiofa" to me, she lost husband and baby on that flight, so her nephew Pavlik became a lot like a son to her, especially since his parents did not survive WWII. Tiofa (actually the name means "aunt") was a good friend of my mother's and she travelled frequently to Moscow all through the years, when very few people did, and every time she visited Pola, thus became the link between my mother and Pola. She took photos from our family to her and brought photos back, etc. Later on, not long before my mother died in 1964, my mother and Pola corresponded again, open postcards, written in Russian, I don't believe I have any of them any more.[1]

Pola had two children, Misha and Inna. I never met them, we shared the Jonas grandparents, who evidently travelled to Russia a few time. I don't believe they ever came to Berlin, my father went to visit them ever so often and I was there (=in Lodz) twice, once when I was seven and the next time when I was fifteen. I still remember they had my pictures and Misha and Ina's hanging over the sofa in the living room.

Inna Pistrak's Memories:

I know that our family fled from Poland to Moscow in 1915. I think Fanya was not married yet. A gifted pianist, she studied at the Moscow conservatory with one of the best professors. My mother Pola met the Pistrak family in Moscow again: she knew them as a child since both families spent summer in Lithuania.  In 1918 my parents got married, and in 1922 they gave birth to their first child, my brother Mikhail (Misha). 

I don’t remember when exactly grandfather Herman and his family returned to Poland.  But I know that Fanya was crying bitterly, she didn’t want to leave Moscow and the Conservatory. I often think that if she had stayed she would have escaped the torture of the ghetto and the Auschwitz. But she could also end up in Gulag, as many others. Who knows… I remember that we got the chance to send food to Poland, to the ghetto, when Stalin and Hitler were good friends yet, in 1940-1941.

Notes:

1. Mom was mistaken, as we do have some cards from Pola to Magdalena; see below.

2. Her daughter, husband, and granddaughter.

3. Don't know to whom this is a reference (not Aunt Fania, since she was killed by Germans). Would seem to be someone else who lived in Moscow, since Pola read Granny's letter to her.

Geni data:

Birth: November 17, 1894

Death: February 13, 1983 (88)

Immediate Family:

Daughter of Herman Jonas and Klara Jonas
Wife of Yakov Pistrak
Mother of Mischa (Michael) Pistrak and Inna Pistrak
Sister of Rafal Jonas and Fania Uryson