Birthdate is unlikely to be forthcoming, as there were no birth certificates at that period, and only the baptism was recorded.
Sources
Parish baptism register (Ilfracombe) via findmypast
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DNA Connections
It may be possible to confirm family relationships with Mary by comparing test results with other carriers of her ancestors' mitochondrial DNA.
However, there are no known mtDNA test-takers in her direct maternal line.
It is likely that these autosomal DNA test-takers will share some percentage of DNA with Mary: