oh my god they were roommates
 
When Rarity decided to move to Manehatten to pursue her career on Bridleway, her little sister, just out of school, came along with her. Sweetie Belle didn’t really know what she expected, but one audition lead to one small role, and soon she was starring in Hoofilton with Rarity. The two sisters rose to fame in their roles as Angelica and Eliza (I cannot make any horse puns here I am sorry). During her run on Bridleway, Sweetie didn’t expect to see her old friend Tender Taps as a part of the ensemble.
 
Taps explained how he had moved here with his friend Pound Cake. Taps to pursue a career with his dancing and Pound to start his own restaurant (cooking is his forte, but he discovered early on that he was SHIT at baking).
 
Taps and Sweetie grew very close through their career and became the best of friends. They were almost always seen together in public, and gossip started, and ponies soon began asking if they were dating. They wanted to tell the public that both of them were gay, and definitely not dating; but, their publicists thought that this would be a picture perfect love story to keep the public entranced. So, they went with it.
 
Tender Taps soon came to his fake lover with a dilemma. He finally realized he was in love with his big, goofy, chef roommate. And Pound (knowing Taps’s situation with Sweetie) had admitted his love for Taps and told him to talk to Sweetie about it. Sweetie Belle wanted Taps to be with who he loved, but their publicists insisted that they keep up their act for the public. The two performers, being young and not really wanting to risk seeming non-compliant to their agents, continued to keep up their facade.
 
Sweetie Belle met many new and many familiar ponies at the galas she attended. But she didn’t expect a familiar face from grade-school to appear again. Diamond Tiara, Sweetie Belle would learn, was now CEO of her own company. Sweetie smirked and commented how she always had an affinity for bossing ponies around. Diamond had seen Sweetie perform and insisted that they catch up sometime. And so they had dinner one night. And one night lead to another night. And another. And another.
 
Diamond understood the circumstances. She knew that Sweetie had thousands of fans to appeal to. And Diamond wanted to keep an “independent, powerful mare” image for her company (but she also just really wanted to cuddle with her new girlfriend). So, Diamond Tiara and Sweetie Belle are in the same relationship that Tender Taps and Pound Cake are. They’re roommates. Just roommates.
 
The four often go on double dates (they always demand round tables, so that everyone can sit next to their actual partners while the Bridleway Sweethearts are still close). They’ve actually all become very good friends. Pound is teaching Sweetie how to cook (Diamond says that she has NOT improved any). Taps is currently teaching Diamond how to dance (She’s a much faster learner that Sweetie is). They may be in a complicated situation, but they make do, and everyone is pretty happy.