Martha May Briggs Fletcher(1847-1939)

Martha Briggs was my great great grandmother, she married Joseph Kennard Fletcher(1842-1916) in Philadelphia. They had six children:

Robert Briggs Fletcher (1866-1934)
Benjamin Kennard Fletcher (1868-195?)
Emma Fletcher(1870-1923)
Charles Mann Fletcher(1880-1973) (My great grandfather)
Mary Fletcher Smiley(1882-1956) Married David Smiley
Emma Fletcher(1886-1950(?)

all these Fletchers are buried at West Laurel Cemetery in Bala Cynwyd, PA

I'm trying to determine who Martha's parents were. I believe her father was a Robert Briggs from Ireland, as I found a census record in Philadelphia that had a Martha the right age with a father(relationship not listed, but he's the right age to be her father) but no possible mother listed.

The online Philadelphia death records/obits don't go as far as 1939 and I haven't tried to order a possible obit from the Free Philadelphia Library yet.

Any other suggestions? To be honest, it's been a while since I focused on Mary, so there may be something simple I'm missing. :)

thank you!