A/N: This is my (probably pathetic) attempt at capturing the brilliance of this amazing companion. If it sucks, feel free to let me know.
Donna Noble was the Doctor's best friend.
At first, she was determined to keep it that way, especially after hearing what he went through with his last two companions. She was determined to be there for him as only a friend could.
But as time wore on, she began to feel more for that skinny man in the brown suit.
She noticed how distraught he was when he thought she was leaving during the Sontaran fiasco.
She helped him accept the existence of Jenny, and later get over the loss of her.
Donna would be lying if she said she didn't feel anything when she kissed the Doctor to save his life.
She was just a little bit jealous of River Song, and guilty that she wasn't on the bus with the Doctor when the creature stole his voice.
All this time her feelings for him grew deeper and deeper, but she never said anything because she thought he still loved her.
And so when the stars went out and the Earth was stolen, and Rose returned, she kept silent and suppressed her emotions, because she saw how happy the Doctor was as he and Rose embraced.
She loved him enough to let him go.
But then he left Rose behind again, this time with the half-human Doctor.
Donna had renewed hope; she didn't expect that hope to vanish as quickly as it had come.
Rather than allow her to die, as she would have wanted, the Doctor wiped her memories, and killed the DoctorDonna.
Before she went unconscious, Donna only had time to regret what was never said.
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