How they first met: They first met when Aria decided to scout the Battle Maison for potential new performers. She was captivated by the four sisters’ show-stopping talent at both battles and beauty and eagerly invited all four to try out being performers. While the other three all declined, wanting to focus on the Maison, Evelyn was struck by how confident Aria seemed and decided to take her up on her offer, wanting to grow more confident herself.  
Where their first date was: After hours of hard work and preparation, Evelyn succeeds in winning enough Princess Keys to enter the Master Class. Aria is so happy for her protege that she insists on bring Evelyn out to dinner to celebrate. Aria might be embarrassed to admit it, but working with Evelyn and helping her overcome her shyness, she’s really started to grow fond of the other girl. She doesn’t outright say the dinner is date, but Evelyn catches on and is blushing furiously throughout the whole thing.
When they had their first kiss: They have their first kiss after Evelyn loses the Gloire Showcase Master Class. Evelyn is devastated that she made it so far only to lose to her mentor, but Aria encourages her that she’s done amazingly well for someone who’s only been performing for a year, and besides, even if she lost to Aria is the showcase… she still won Aria’s heart! While Evelyn is still a bit confused from those words, Aria leans in for a quick peck on the lips.
Who cooks: Both are very good cooks, though they have different specialties. Evelyn tends to make more comfort-food dishes, bursting with flavor and always a favorite, while Aria likes to get a bit more experimental. As Evelyn is now fairly busy with her Gym Leader job, Aria tends to cook more often since her schedule can be a bit more flexible, though they’re still both high profile trainers so who’s cooking really varies. 
Who proposed: Evelyn, perhaps surprisingly. It took a lot of support from her sisters and some psyching up in the mirror before hand, but Evelyn proposes to Aria after they’ve been dating for about a year and a half. She doesn’t want it to be a big affair, so she chooses a quiet, out of the way location so the media don’t find out right away. (They quickly notice the new rings on the couple’s fingers later on though!)
The dominant one: Aria for sure.
Their favorite pastime together: Both being high profile, it can be a bit hard to get time to themselves, so one of their favorite activities is heading out into the countryside for a quiet day trip. They enjoy going for walks in nature, having a picnic, playing with their pokemon and Vesper once she’s born, as well as taking plenty of pictures to preserve the happy family memories.
Who kissed who first: Aria kissed Eveyln!
Who is the flirt: Aria, though it’s more playful than anything. She thinks Evelyn is super cute when she blushes.
Who is the romantic: Both are kind of hopeless romantics, so anything along those lines is a favorite. Candlelit dinners, buying flowers, the works.
Who wakes up first: Aria usually! True to her name, Evelyn is a bit of a late riser.
Who comforts who the most: Evelyn has made a lot of progress with her self confidence, but she still suffers from plenty of nerves before any big event, especially Gym Battles. Thus, Aria tends to comfort her the most, giving her pep talks and ensuring that she’ll do her best.
The cuddler: Aria.
The big spoon: Also Aria!