Stalker Celica is both funny and terrifying! MAKE IT WORK!
I think of all the core group being stalkerish, Celica fits it the best, especially if you pursue a relationship with Sam. Like, "why is the MC hanging out with HER more than me?!" Those two really have a rivalry going... I don't see either succubus being a stalker, Maya might just because she's hoping for more headpats, and Aspasia might just because she finds you interesting. Depending how much you tease Ina while she's in the group before heading off to Selendis Ina might stalk you for revenge pranks!