I've been at an internship for the past 9 weeks. At the beginning of the period, I became close with two other interns, Alex and Sue, as we all started on the same day. However, as the internship has progressed both Alex and I have realized that we don't enjoy hanging out with Sue. She has a toxic personality and what I would consider to be narcissistic tendencies. Interacting with her in group settings is always fairly awkward - she always interjects herself into other people's conversation, tries to be the center of attention as much as possible, makes incredibly forced jokes and gets upset when nobody laughs, etc.
Over the past week or two, Alex and I have been trying to distance ourselves from her. We've been messaging her less and have been hanging out without her. However, Sue hasn't really gotten the message. Just yesterday she was asking us when we were going to visit each other after the internship ended (neither Alex nor I want to interact with her after this internship).
How can I make it clear to her (without being overly rude or hostile, as she still is coworker) that I would like to have a strictly professional relationship with her? I would expect repercussions in the workplace to be relatively limited as we do not work in the same department or on the same floor, and don't interact in the workplace unless Sue makes an effort to come find me and talk to me.