You can clearly see the difference:
Kanan - gets invited by Kyougi on a date because it's natrual since they're a couple.
Jeanne - screams, stomps on the ground and demands everyone else accomodates her third wheel. Doesn't even ask if Kyougi wants to go on a date with her.
Really, a girl who throws a tantrum and has the gall to feel entitled to going on a date with another girl's boyfriend. She's beyond selfish.
And to top it all off, the author had to make Kanan extra stupid to fall for Ami's guilt trip.
The whole world had to bend over backwards for this stupid scenario to take place.