Why were Marcus hostile towards Selene ?.
He had absolutely no reason for it, except for the script to have more drama.
Selene was the one who disclosed the scemes by victor and also quiet possibly
saved with Victor AND Marcus from death by unveiling the attack and takeover
by the werewolves by the aid of Kraven.
Had Selene not set in motion these events, the werewolves would've more then
likely dug up all the sleeping elder vampires and killed them all once
they got access to their hideout by Kraven.
It was only logical that Marcus should've asked Selene for some blood to tell
if she was lying or not, but since he already had the memories from the kill
man who's blood woke up Marcus, he should know what was going on and not
been hostile towards Selene.
I really don't like when they make movies where the characters makes decisions
that has absolutely no logic.