Normally opposite-gender characters can only get the additional Love bonus of 5 points per turn by waiting adjacent to each other. If another female character waits adjacent to the first female in the pair, they will steal the adjacent Love bonus from the first female if they have higher priority for the male.
This effect stacks for multiple males and females. The most useful application is to have the benefiting female wait 1 square diagonally from the male, with two lower priority females in between them to make a square-shaped formation. That way, the female will steal both lots of the adjacent Love bonus, allowing them to gain an additional Love bonus of 10 points per turn instead of 5, thus speeding up Love growth.
This phenomenon is also the cause of a bug that allows Seliph and Julia to fall in love by as early as Chapter 8, by using Lana and Larcei as the in-between females. However, to utilise that bug, one must not reset once the Second Generation has begun, otherwise Lana and Larcei's priority with Seliph will become equal with Julia's.