Your great, great grandfather Tobirama Senju never trusted the Uchiha and that trait was passed down to your grandfather. Your grandfather passed that to your father and he would be damned if you would be acquainted with one.
Just so happens that you fell in love with one, Uchiha Itachi. Although the two of you share a strong relationship but you sense him pulling away. One night sealed his fate and reputation – you followed him there and you still do, even as Itachi has evolved to an Akatsuki member. [sorry it’s so long! originally posted on my ao3]
“You know you’re my special girl, right?” your father was knelt down to meet your level and smiled as he rubbed the top of your head. “I entrust the future of the Senju name to you.” he stood back up and looked down as his demeanor took on a more serious tone. He raised a finger and placed it on the tip of your nose, “No matter what you do, beware of the Uchiha, [Y/N].” Your father was the son of your grandfather, who was the son of Senju Tobirama and you were the last of the direct Tobirama bloodline. This caused your father to feel the weight of leaving the legacy of the Senju clan to you.
He raised you on his own as your mother passed away in childbirth, an emotional burden that the two of you carried.
Your father kept you under his watch constantly as he did not trust the outside world and did not want you to be tainted. Your clan was known as being the “clan of a thousand skills”. The wrong people could see a naïve child as being the best possible opportunity to use this power for evil. So, that is why your father kept you by his side at all times. This meant that you were not allowed to train as a shinobi like the other children of Konohagakure; he left that training up to himself. Who else to train a Senju than a Senju?
That also meant that he passed down the distrust of the rival Uchiha clan. Great grandfather Tobirama taught Uchiha mistrust to his son, who taught it to his, who then tried to teach it to you. You were headstrong however and did not believe that all Uchiha could be cunning and untrustworthy. No matter how much you argued with your father, it never got anywhere; so you learned to keep quiet on the subject. Unbeknownst to him, just the same as his great-uncle had befriended an Uchiha, you had as well.