all we know about her points to that she has no motive period, not just yet. But if you have any clues from the game i'm open to hear them. But i dont see it even less with the meta knowledge we have about her from what Cosy told us.
Here is all Rachel said (in that interaction).
Rachel "I-I..."
Rachel "I-I thought that... You, uhm... And them..."
Rachel "I was wrong, so I'll just go..."
Rachel "P-Police..."
Rachel "P-Please don't... I didn't mean to... I..."
Rachel "I knew it..."
Rachel "You're gonna make me do all kinds of perverted and deviant acts against my will..."
Rachel "That's..."
Rachel "Y-You can do whatever you want with me."
That is it (I got rid of all the stuff the MC and the other girls said). It appears she thought in her little mind that things were a certain way, and they weren't when she heard the interaction with Hannah. Thus she was wrong, but wanted to get her proof. Honestly, Rachel appears to me to be not the sharpest tool in the shed. As for if she stole it the booklet? I don't know. She might have. But as this went back to when V10 was released (or was it 9, I forget when this storyline occurred).
* Rachel - has something to prove, might have stolen it.
* Other girl in cafe - doubtful, they would be punished, and not speaking up before Hannah was punished is a bad move. This is pre-Catherine working, fyi.
* Annabelle - Possible, as she is there all day, and appears to want that favor. We don't know about her to know if she will steal.
* Rando we haven't been introduced to at this point - Might be someone who needs something, and is a possibility.
That's about it. At that point. We know some other things in the days since this happened:
* Catherine has stated what she wanted the MC to use her favor for (when she was caught with a limited amount of cash).
* No one claimed the ticket, as of yet, several days after the raffle finished.