Shapiro/Shapira connection to Baal Shem Tov #rabbinic

Shmuly Noe

I am looking for information on how my great great great grandmother, Bluma Averbuch nee Shapiro (born 10 September 1887 in Mezeritch), daughter of Zev/Willie/Volf and Chana Faigela Shapiro is descended from the Baal Shem Tov? She had a brother called Alexander Chaim Shapiro, died in London in around 1949, who was a Trisker Chossid. 
Anyone who has any further information or links, I would be very gratedful.

Shmuly Noe