Marcella

 is one of the inhabitants of Point Lookout. She is a Christian Missionary from the Abbey of the Road who has set up shop east of the Pier in the Disaster Relief Outpost.

Her terminal mentions describes her travel east from the Abbey to the Commonwealth. Apparently she had to leave the latter rather quickly before she had to suffer the consequences of her "doing what she could". From there, she took the Duchess Gambit south to Rivet City where she met up with Father Clifford before finally arriving at Point Lookout.

Related quest: The Dark Heart of Blackhall
She opposes Obadiah Blackhall in his attempts to recover The Krivbeknih and asks the Lone Wanderer not to give the book to Blackhall. Although her efforts ultimately lead to her demise, murdered in her tent, she leaves a holotape begging the PC to take the book to the Dunwich Building and destroy it.

Appearances
appears only in the Fallout 3 add-on Point Lookout.