her mother was a changeling and her father a unicorn.
Her mother got lost while an attacking a Pony village with some others. She got hurted at the wing and wasnt able to fly back to her home. She was found by the father and they both fell in love. When she got pregnant he gave her all his love and so he stopped loving her. He sent her away, luckily she was able to fly again, but as she had given birth to her child, she was banished. They kept the child(OC) because they thought a half unicorn could be usefull.
Of course the changelings treated her worse because she was diffrent, so she got a special connection to the nature( Fascination for Beauty of flowers, animals as friends)
She heard Storys about Canterlot and the Ponys who live and ran away.
She reached the forest near ponyville and got bad doubts if they would recognice she was a changeling and maybe sent her back.
but then, she met a fiew fillies (also the cutiemarkcrusaders) which were playing and they didnt.
Applebloom invited her to the Farm where she met the Apple Family. Then, Applejack wantet to talk with her alone and she thought maybe she had recogniced that she was a filly. In fact, Applejack was just thinking she was homeless because of her appereance.
they found a Family for her so far the end...
I just sum it up so i lost Detail...
Im still working on the Story to make it less dramatic
But so far i hope it helps you