I know this might be pushing it a little butā¦.
In Episode 6 āThe Bet Galaā after Mary and Ryan get up from the table, Riri is seen walking towards them in the background and her gaze follows Mary as she walks past her and leaves the room. Riri is holding what appears to be a deck of cards in her hands.
What if she was trying to ask Mary to the Bet Gala by challenging her to a card game? An āIf I win I take you on a dateā type of thing, but Mary left before she could challenge her.
Their next scene together Mary and Ryan are in the gambling den and they see the bet board says āODDS 2/1 | MARY + RIRI @ BET GALAā. Thatās when Mary seeās Riri sitting on the stairwell and walks over to her. Riri then asks Mary to go with her (in her own way). My theory is that the bet board was Ririās back up plan. Her original plan was to beat Mary in a game because she knows how much Mary loves games. This was also around the time Mary stopped cheating, so Riri wouldāve had the advantage over her. Spoken like she wasnāt second in the whole school, but you get what I mean.
Hereās a screenshot of Riri holding what I think is the deck of cards.
I donāt care if it makes sense or not, this is now my favorite headcanon.