I assume the family was RC. I located one possible lead for Bridget.
On the subscription site Roots Ireland, there is a February 23, 1851 marriage in Rathdrum RC church for a Bridget Harman of Ballydowling to Michael Cromeen also of Ballydowling.
I did not see a Mary Harmon/Harman marriage in Rathdrum and no marriage anywhere in Wicklow for a Lawrence Harmon/Harman.
Lawrence Harmon was not listed in the Griffiths Valuation of 1854 in Co. Wicklow.
I also did not see any good leads for death records for Mary or Lawerence.