Singspiel is a mentally disturbed unicorn who ran away from home. Her mother disappeared when she was young and was abused by the man she was left in care of. She tries to socialize and gets upset by this, so she teams up with a seemingly evil pegasus in hopes to find and finally meet her mother.
SPOILER/WARNING: Begining in the third chapter it is going to be in sections based on which mane 6 pony she interacts with. And, Singspiel points out their character flaws to get said pony to kick her out so she may leave without upsetting the others, raising questions, search parties, ect.
Please do not get butthurt by this. It's part of her character.