I am not sure if there was 9th one. Possibly the dev decided to combine Caly and Others into one, to hide Caly as secret love interest, due to her initial introduction as NPC. The reversed question mark, if it was her spot, was going to out her being real rather than AI early in the story. The one right next to Alex was Nova. The last was that was Others, assuming the reverse ? was Caly was going to Eva once more.
As for potential 9th love interest, there aren't too many options. Charlote possibly to get info from Axel but now we are doing with him instead. Eva due to her dialogue about "what is real" and "prefering Eternum over the normal world" could have had her own story arc revolving having even bad family life / situation irl but then Alex has the same arc. Eva seem the most likely one, to be honest. Matt, she apperead in 0.3, so it's possible that there were bigger plans for her that were revolked because it didn't make sense for Orion and Nova to be nice to her after what she did. Matt, unlike Eva, returned for something beside gag and seem to have relavence to the story, the option to give her money being required for perfect run.