Final answer:
The most likely source of bleeding in this woman is placenta previa, which occurs when the placenta partially or completely covers the opening of the cervix.
Step-by-step explanation:
The most likely source of bleeding in a 32-year-old G3P2 woman at 40 1/7 weeks gestation with regular uterine contractions, bright red, bloody discharge, and a friable cervix that bleeds easily is placenta previa. Placenta previa occurs when the placenta partially or completely covers the opening of the cervix, leading to profuse vaginal bleeding. It is the leading cause of antepartum hemorrhage in pregnancies after week 24 but prior to childbirth.