If Mason ever tried to interact with Morgan, she wouldn't really act unnerved by him, she's generally neutral towards people she doesn't know well. That said the knife is used for ritual and for gathering supplies, so she would only bring it to school on the rare occasion that she had to go somewhere close by right away. She'd be too worried it would be confiscated to just wave it around, also. So he'd only really see it if he was very much right up in her business and looking in her bag or something to that effect. 

As for E, I think they'd have a sort of friendly banter, sometimes talkING about the goings on in school. Morgan's not one to make really fast friends, but that doesn't mean she's not friendly. She'll most likely acquaintances with the majority of other characters. There is, of course, the possibility of becoming closer, she's just a little reserved unless someone is really trying to become closer.