Hagrid had only, that morning, advised of the death of Aragoga, and if Hermione was honest, she had no desire to see an acromantula. Whilst her fear of spiders wasn’t quite as prominent as Ron’s, she found her curiosity did not outway her discomfort of seeing such a large spider. Especially given that it would be outside hours. Not to mention that she had prefect duties, something Ron was very eager to be a part of for once.  