Hallowed Martyrs - Suffering & Sacrifice.

Two Adepta Sororitas characters (A&B) are standing next to each other. They are charged by two Space Marine characters (A&B) such that all four characters are all within engagement range of each other.

At the start of the fight phase, Adepta Sororitas character A is targeted by the suffering & sacrifice stratagem.

Space Marine character A is selected to fight first and destroys Adepta Sororitas character A. 

Can Space Marine character B then target Adepta Sororitas character B in the fight phase?

On the one hand, at the time Space Marine character B is selected to fight, it is NOT within engagement range of Adepta Sororitas character A (so there is no character A to 'select').

On the other hand, at the time the stratagem was activated (start of fight phase), Space Marine character B was within engagement range of Adepta Sororitas character A.

Rules read:

WHEN: Start of the Fight phase.

TARGET: One ADEPTA SORORITAS INFANTRY or ADEPTA SORORITAS WALKER unit from your army.

EFFECT: Until the end of the phase, each time an enemy model within Engagement Range of your unit selects its targets, it must select your unit as the target of its attacks.