The accident happened around 6:00 p.m. near the Bryn Mawr train station last Friday.
Officials say Michelle Rein, 44, of 22nd Street in Center City Philadelphia, was trying to catch her dog who had gotten loose, when she went onto the tracks and was struck by an inbound R5 Paoli-Thorndale train.
Rein was pronounced dead at the scene.
The dog was unhurt.