Maria Hein's mother is Bertha Hein. If she is not Maria's mother, she is a close relation of her parent's generation such as an aunt or wife of an uncle.
The location of the Carrie Solle's death and that of Bertha Hein is the same location, separated by only 9 months worth of time. Maria's surname before marriage was Hein, matching the name of Bertha Hein. It is unlikely an unrelated Hein would live at the same location as Maria. Because Bertha's birthdate is April 1807 and Maria's is 1843, the inference is that Bertha is her parent's generation rather than grandparent's or her own. The most likely relationship would be her mother, though other relationships are also possible.