A side-story in the manga adaptation, where Louise is dosed with two different kinds of Love Potion simultaneously, and their interaction causes her to become irresistably attracted... to girls; all girls.
Louise and Siesta.
There was that time Louise crawled into Saito's bed, but it turns out Siesta was sleeping there which Louise wasn't aware of, and she immediately grabs Louise (thinking that she's Saito) and pulls her into a kiss while both are still asleep. Louise appears to like it and places her hand on Siesta's Gag Boobs... which is when she notices something's wrong with this picture...
The those times where Siesta pulls Louise to her chest to initiate some Marshmallow Hell for no real reason when getting too into a fantasy of her and Saito...
In season 4 episode 5 Siesta and Louise sleep in the same bed because Saito and Louise had a fight so Saito decides to sleep in another room.
After Saito's victory over Guiche, he becomes popular with the commoners and some nobles in the school, both male and female. Marto, the school's head cook is especially in awe of Saito for his victory and gives him free food because of it. He also affectionately calls him "Our Sword", embraces and even attempts to kiss him on multiple occasions.
In the last episode of season 2, Saito gives a sleeping Louise to Julio, who promises to watch her while Saito's out doing battle. Saito tells him he's fighting for Louise's sake because he loves her, and Julio is so touched by this that he gazes at/says to him with much adoration: "I wish to tell you I love you too." He also said in a seductive tone of voice to Saito that he wants to kiss not only Louise but Saito as well during a sword fight with Saito.
Scarron, a Macho Camp inn manager, who tends to hit on his male customers and who has also taken a liking to Saito, saying that he is "just his type." This also includes one instance where Scarron runs really fast towards Saito and Glomps him, holding him close to his body and releasing hearts. When he first meets Saito he gushes over him and states "what a cute face" while getting close to his face with his lips puckered. Going back to the Love Potion incident during Season 3, Scarron becomes influenced by the Love Potion, promptly Glomps Saito upon seeing him and tries to plant a kiss on him while saying "I'll serve you well!" In episode 4 season 4 Scarron calls Saito an "attractive guy".
Tiffania (who has the biggest Gag Boobs out of all the girls in the series that just about everyone has stared at) who gains about three female admirers by the end of the third season, and before that said female admirers tended to fawn over their token princess...
Season 4, Episode 6, when Henrietta gropes Louise's super flat chest. They are fighting over Saito in the middle of a hot spring, buck naked. Doubles as Foe Yay as well.
Squadron captain Agnes and Princess Henrietta, combined with Tomboy and Girly Girl. Agnes clearly states that once she gets her revenge (which she eventually succeeds), she will protect the princess even at the cost of her life. In season 3 and 4 (episode 2 and 3), they are seen together more often.
In the fourth season's OP, Louise gets licked on her face by a new, evil, purple-haired girl named Janette and the girl hugs Louise close to her with a blushing Louise struggling to get away. And in episode two Janette tricks Louise by pretending to be a plebeian, gets close to her face, and licks her again. She also touches her face and says that if things had worked out different they could have been friends. She also calls Louise "cute and innocent" and practically flirts with her.
In the third season, Kirche and Louise. Not only does she make a truce with Louise, she even gives her a Marshmallow Hell hug. To top it all off, she tells her that after they rescued Tabitha, the two girls should go to Germania (Kirche's hometown), so Louise can be her personal maid.
Guiche and Saito. By season three, Guiche and Saito become good friends. In the light novels, when Saito was presumed dead, Guiche erected a statue of him in honor of his friend. Unfortunately, Louise and Siesta accidentally destroyed it. Also, in the manga he wanted to make it up to Saito after their battle with roses but was too embarrassed to give them to him directly so he tried to ask Louise to give them to him.
Tabitha and Kirche. They are very close and Kirche was really worried for her friend when she was in trouble and did her best to save her. Also, after learning of Tabitha's Dark and Troubled Past and seeing her haunted by nightmares in her sleep, she decides to lie beside Tabitha and embrace her, telling her everything will be alright. In episode 3 season 4 after Tabitha comes back from fighting Joseph Kirche is shown to tenderly hug a blushing Tabitha to her.
Louise even gets a few moments with her sisters Eleanor and Cattleya who love and care for her very much, fuss over her, sometimes initiate some Marshmallow Hell, and in an official art Cattleya even lets Louise use her as a Lap Pillow.
Irukukwu "Sylphid" and Tabitha. Irukukwu is very affectionate towards Tabitha, her "Onee-sama", and fawns over her. Tabitha takes it in good humor.
In season 4 episode 3 Siesta glomps Tiffania after the latter uses her magic to make some mooks forget that they were supposed to make the stone explode.
Judging from Season 4 Episode 4 there is a slight moment between Kirche and Montmorency with Montmorency being on top of Kirche in bed. Turns out they are just playing around while discussing something.