That poster on the wall is used in plenty of games as decoration to make room look lived-in and not completely barren. And yet you have decided that this is a carefully planted clue that can reveal a character's deepest desires. You're making mountains out of molehills, and jumping to absurd conclusions from two lines of dialogue and a random poster on a wall.
Camilla: This thing we're doing, it's for college, right?
Mona: It was never about college for me.
Let's think of a few possibilities for these two lines here. Riona is doing it for the drugs. Riona is doing it as an attempt to escape her unhappy life. Riona is doing it to help her oldest friend. Riona is trying to become a prep's trophy wife.
What's most likely? That she's doing it for a combination of the first three reasons. Quinn is her oldest friend and Riona knows how desperate she is. When not out partying and doing drugs, Riona is often found alone and looking unhappy, depressed, or even scared. What's least likely? She's trying to land a rich guy.
If a prep is going to go looking for a trophy wife, it's not going to be a heavily tattooed girl with a drug habit who prostitutes herself. They are going to want a girl who the other uptight prep snobs will view as an acceptable and respected member of society. This is why we see Tybalt going after Jill and not any of the HOTs.
And what reason do I have to think that Riona was doing "this thing" for Quinn? Well, I have the entire conversation that you cut two lines from.
Riona complains about Quinn, calls Camila her best friend (which is huge because up until now that's been Quinn), says she will quit helping Quinn if things don't turn around in a hurry, and says that she doesn't have a future in college because she's dumb (which is what Quinn told her to keep her obedient). Camila acts like any true friend, and reassures Riona that she is smart and fully capable of graduating because she has been doing just fine so far.
There was not a single thing in that conversation that would lead any rational mind to suspect Riona of having planned to become a kept woman by landing a wealthy prep kid. Nothing. It was all about how Camila and Riona are become best friends, and Quinn is becoming isolated and desperate.
That whole conversation was about Quinn losing control and spiralling downwards, as is much of the game.
The day after the party we see a scene where Heather complains to Riona about the "misunderstanding" with the DIKs, and she starts questioning why they were even there to begin with. Riona tries to make her believe that they needed more money for the increased members, but Heather doesn't buy it. She mentions the fees they have to pay (which is in stark contrast to the "rumors" of free tuition spread by Quinn to get recruits). Then she begins talking about how Sage should step down as a leader.
The next scene is a strung out Quinn calling her dealer to say that she can make a payment that she was late on. Camilia enters the room and tells her that Mona is out. Quinn is scared and angrily asks if Mona is going to be a problem. The next chapter starts with a flashback to Quinn's childhood with her junkie parents, and a short scene later we see Quinn confronting Mona.
Mona: I thought I could, but as soon as he started touching me I felt sick.
Quinn: Pathetic. This isn't the same go-getter I talked to before. You know what you agreed to.
Mona: But I don't want it anymore. You never told me I had to do old guys!
So we know that Quinn told Mona that she had to do guys, just not old guys. Mona then promises not to say anything about it or the drug deals, which is news to Lily who is still in the room because Quinn failed to intimidate her into leaving. Quinn then issues a thinly veiled threat to Mona. Quinn later gets jumped and robbed. She talks to Riona who tells her that she feels like she's being followed. Quinn ridicules her and Riona starts to complain about how this isn't what Quinn promised it would be like. We later see Maya confront Quinn about the tutition she promised her and Mona, and after Mona backs Quinn's lies, Maya slaps her and storms out. The chapter ends with Burke deleting Mona's scholarship application and we see Mona leaving campus with her bags packed. Quinn's problems continue to build when Sage hears of the slap and demands the Quinn go make nice with Maya, who will later tell Sage that Quinn did the exact opposite.
Mona's departure leads to Camila becoming closer to Quinn, Quinn being more distant from both of them, and to Lily learning about Quinn's dealings, and also to Sage starting to rein in Quinn. Nothing anywhere has anything to do with any of them trying to become a trophy wife. It was all about Quinn being a stubborn incompetent moron who alienates her closest friends and is setting herself up for disaster.
