Mia: Don’t give up, Rarity. You have the evidence right there.
 
Rarity: But it’s clearly her mane that was found at the scene!
 
Mia: Look at it again.
 
(Rarity looks at it again, and sees the straight line where it was cut.)
 
Rarity: Of course! (pointing her hoof) OBJECTION! (sends Edgeworth flying) Your Honor, I would like for you to look again at this rainbow mane found at crime scene.
 
Judge: Yes, what about it?
 
Rarity: Look at the ends, it’s a straight line.
 
Judge: Oh, you’re right!
 
Rarity: Nopony loses their hair in a chunk, they were clearly cut with sheers.
 
Edgeworth: Utter nonsense! She could have just cut that hair herself.
 
Rarity: And why would she want to leave behind such obvious evidence? Whoever wrote that note managed to sneak into Rainbow Dash’s room and cut this piece of her hair.
 
Wind Rider: That’s ridiculous, I didn’t use sheers!”

And then she hastily restarts to prevent Rainbow Dash from being declared guilty.

@WinterCutieMark  
Look at the clock: There’s, like, another 20 minutes of in-game time until face-in-hooves time.

Time to put your face in your hooves, almost give up and then at the last moment realise what you need to do to prove RD was in fact framed.

@RulerOfIce  
That can happen after she reloads her save with no damage to her penalty bar.

Now then, Rarity. Time to think outside the box.