Twilight was reading while her little daughters, Spectra who just turned 5, and Astral who was 2 years old, played happily in the ground. She was flipping through an old spell book, when a spell caught her attention “Fire manipulation?, i never heard of this one before…how about we try it? Spectra would you like to see mom make a spell?” “Yes mother!!” she followed the steps as little Spectra watched in awe as a little spark flied from the fireplace to the front of her mother “Heh, it worked!!” Twilight began to play with the little spark…until an idea crossed her mind, what if…what if she could do a light force? like the sun? She started to expand the spark, until it was now the size of a ball ‘yes, could i make it as big as the sun? we could fight her… with it?” It was getting pretty unstable now “Mother…?” just in that moment the ball of fire got out of Twilight’s grasp, and directly to her daughters, she performed the spell again, but since it was unstable it fled straight to the side of her face, the last thing she heard before passing out was the screams of Spectra and Astral crying.
 
She woke up in her bed, with her wife by her side…she looked mad, but also worried. “What where you doing…dear?! “ “Just trying a spell…” she became wary of what she said “ just to entertain the girls, are they ok?” Nightmare sighed “yes, but Spectra was pretty shocked” “my poor baby…could you tell her to come here?” Moments later Spectra went inside, with her head hung low “Spectra? Come here dear” she crawled into the bed, but she wasn’t looking at her mother “Mother…was it my fault? d-did i distracted you?” “what? no, no, it was just your silly mother…stay here with me and rest a little” she gave her forehead a kiss, and they went to sleep.
 
Little fun fact! Astral can grab things with her hair! Since in the first episode Nightmare Moon can do it, i thought that her daughter could as well!  
Btw, the reason for Spectra being an alicorn is because Nightmare Moon (remember this is still Luna’s body) carried her, so the alicorn gene passed to her.