Final answer:
Abek volunteered to come to Burgberg after George asked him to. Gerda feels responsible for Abek's coming, and she tries to make up for it by showing him love and care during his last days.
Step-by-step explanation:
Abek volunteered to come to Burgberg because George had asked him to come if he got killed.
Gerda feels responsible for Abek coming because she sent George a letter requesting that he ask Abek to come.
Whether or not Gerda is responsible is subjective, but she does try to make up for it by showing loving behavior towards Abek during his last days.
This can be seen when Gerda is described as being loving and caring towards Abek, expressing her remorse and asking for forgiveness.