Genealogy / International adoption from 1952 Poland [4]

Hello.

My mother: Janina Kazimiera Piwowarska (original father's name Lesiak but she was adopted by Mr. Wójcik) was born in Koluszki, Poland on 11.06.1946.
Her mother: Aniela Lesiak (father's name Trybel) was born on April 9, 1921 in Żakowice, Poland
Her father: Stanisław Lesiak, born on 13.01.1915 in Żakowice, Poland

My mother for almost 20 years was looking for her own brother, whose mother Aniela gave up for adoption. She found him.
My mother also got adopted by polish couple - Piotr and Stefania Wójcik (I have documents from her adoption)

Unfortunately, my mother never managed to find a native sister who was given up for adoption - Barbara Elżbieta Lesiak (surname was of course changed for adoption needs) - born in Gdańsk, Poland on April 4, 1952 was given up for adoption when she was 3-4 months. From my mother's information, she probably went to a family of doctors from the United States. My mother was a witness to her sister's being taken away

How can I reunite my mother with her sister? Is it possible to contact her and find her? I will be grateful for any suggestions. I will be glad to present any documents that may come imporant in this case.I'm also able to pay for any private investigations

regards
RP