Definitely not 1 ending per girl, Amy has 2 endings, and Sophia has 2 endings.One ending per girl (though some endings tie-in with other ladies), afaik, pretty straightforward on that.
"Bottom right girl" should be Hikari - just going to the poll between afternoon and night should lead into you bumping into her and starting her storyline. Try getting there early afternoon and hit "skip time" until she appears.