Eva's expression turned serious and thougher as Tammy spoke.
"Should I remind you that is your job to help the students in the school? The last I checked, you are our house prefect." Yes, it was a low blow, but Tamzin's immediate superior attittude annoyed her and Eva felt like defending Helios, which was a stranger, compared to Tammy. And by 'our' she didn't mean herself and Helios. She was using the plural on purpose, so that Tammy would understand that wasn't just something between the two girls. No, there was a lot more people involved than anyone of them could imagine.

It helped her a lot to have him there by her side. Just like an ally in a dangerous battle, despite Tamzin being everything less dangerous.
"You know a lot of people... You should know as well everything that happens in here." she started out slowly and very softly. "If we needed to... know a few couple of things, who should we talk to?" Okay, it was nothing subtle, but it should fit her purposes and to start off the conversation.
Because there was no way Tammy would make it easier for her.