The mother's maiden name appearing on 6 out of 8 of baptismal records for Franciszka Zasada's (daughter of Malgorzata) children is "Szachogluchowicz". On the records for Franciszka's last two children viewed-to-date, the maiden name is "Szachacz." I believe that c1847 the family shortened the name (formally or not) to "Szachacz."
Furthermore, geneteka.genealodzy.pl includes a reference to a record of death for "Malgorzata Szachacz" (died 1848, Kruszyn Parish (Akt 37)). I have not seen the actual record yet, but I believe it may be for "Malgorzata Szachogluchowicz".