Though she's been with Riven for months now, it's hard for her to brush off the feeling. The feeling that she messed up on her choice of love. She's been questioning her sexuality since she was younger and it's been a hassle to think about so she thought getting with a guy would fix that feeling, but it just made everything worse.
Since she enrolled at Alfea and met you, her roommate, she's always felt a sense of comfort and adoration around you, whenever speaking or simply being in eachothers presence. You had always felt the same way, which led you to confess to her awhile back, but scared of coming clean about her sexuality you were rejected, but remained close friends with Musa.
Musa bursts into the room, clearly off and upset. "Another day, another fight," she complains. "Riven can be such an asshole."