Some more specific suggestions:
The zombie grabbing Eve's shoulder seems like an important moment to punctuate with a lot of suspense. After she gasps, you can provide more of a delay before the actual shoulder grab. That will give the audience time to realize that an encounter with the zombies is imminent. They need enough time to imagine the worst and get scared. To fill this time, you could show Eve looking afraid or tense or considering courses of action she could take.
You could even slow down the hand grabbing her. You could frame in tight on the hand and show the fingers slowly bending as they grab her shoulder. But that might be really hard to animate...! But essentially, just think about how you can milk that moment of when he grabs her shoulder.
Then when the zombie starts talking to her, you could show some of this with a 3/4 or side view. And maybe even zoom in closer to his face, focusing on his mouth, maybe with Eve's ear also in the shot. That way, the idea is more that Eve knows he's talking because she hears his voice, but since he's behind her, she can't really see what's happening. The character Eve may not be scared, but if the audience doesn't know that right away, they can still get scared. Although I think it would be cool if she did look scared, maybe some wincing with only part of her face on camera.
These are some ideas on how to make her look like she's actually considering joining the zombies. Started out as a rough storyboard and then part way through it turned into something more like fan art! ;D I had way too much fun with that one. Anyway, the main points in that are that when eyes are visualizing and remembering (two important mental actions in this scene) they look off to the character's left. Unfortunately, that's where the zombie is, too. So it might look like she's looking at the zombie. So maybe you could make her default eye direction forward. Like she doesn't even want to look at the zombie. That way when she looks off to her left, it will give the impression that she's thinking a new thought. And basically, you can just stall a little with her being conflicted, before she gets determined and says that she says she will always honor the pact.
The other thing is, she can't really be that determined to honor the pact. Otherwise she wouldn't be having this dream every night for a thousand years. Maybe it should seem more like she's bluffing about how determined she really is? Or maybe lying to herself?
