One last thing crossed my mind. Alana might reappear, but not necessary as a love interest or even a side-story (and her own story with her problems where the MC offers her to cheer her up has gone to the limbo), in the Lisa route, as she is her sister. This gives her space/reason to reappear if something goes wrong (or well?) with Lisa.
She might also reappear (maybe even with Lisa) in the Sandra route, in the crowd of a wedding ceremony, as she was (is) Sandra's best friend (and in this route, that's all she ever was, a distant acquaintance of Sandra we saw three times, exchanged with her ten words, and possibly danced with once).