Okay, so after someone encounters Luci's scent, doesn't matter how much, afterwards say they bump into their crush. If this person like gives them a real friendly hug or a kiss on the cheek or something then boom, they're in love. Or if they're just like walking down the street and somebody randomly runs up to them and kisses them, and they genuinely enjoy the kiss, he or she is in love. 

Or hell even if they just see someone and think "wow he or she is pretty, i wonder what it'd be like to date him/her or kiss him/her" than boom, in love. Does it make sense? D: maybe im too sleepy to explain this haha