I meant it more as a rethorical question, but it seems I wasn't clear enough.
Interstice said:
Erica's been with Rickert for their first apostle encounter and been at his side when fending off monsters. She knows it's dangerous, but she's survived thus far and it's probably given her a false sense of invulnerability.
She also obviously loves and cares for Rickert, and she already declared that she would follow him into danger. When people sense someone they love is in danger, they do irrational things. It may be a trope, but it happens quite a bit in real life.
Also keep in mind she is a child.
Indeed, you have a good point there. Nevertheless, because she is a child, I'd expect her to be more scared, and with all the time they have been confronted with appostles/monsters, she should be more aware how dangerous it can be by now. Yes, love can lead to perform irrational actions; I just didn't like how it turned out. We will see in the next chapters whether this will lead to Rickerts character development (because of Erica's possible death), or just a rescue Erica mission, which feels kinda cheap, and possibly unnecessary for the story.