At the start of Yarra's route the Qum Mood score is set, based on her RP. You can check it with the Qum's reply to Yarra's question how she is willing to help in the gathering:
|≥ 100||12||"Cumdump knows she is Simon's! Cumdump will fuck anyone Yarra wants!"|
|90-99||6||"Cumdump can help a little for Simon!"|
|75-89||3||"Cumdump wants to be Simon's, but she can help a little."|
|≤ 74||0||"Cumdump misses Simon..."|
The only way that she is present in all the scenes only is having an RP score ≥ 100. The "Sleep" action during the route adds 3 points to the score. For each sex scene Qum joins during the gathering her mood is reduced by 3 points.
The scenes are 4 in total: Carnival of Sex, Orc Council, Ogre Scene and Palace Guard asking anal sex with Qum. Each scene with the participation of Qum grants an Empress Approval point.
The most harmless to skip is the last (palace guard) because she lets Yarra's group pass after the succubus hunt. The most important one is the ogre scene because it will grant +5 Fheliel RP much later in the game (after the Erosian Conflict's first phase).
You can check the Mood score by talking with Qum in the room:
|12||"Cumdump will do anything for Simon!"|
|6||"Cumdump will help however Yarra says, even fucking!"|
|3||"Cumdump can help Yarra, at least a little more..."|
|0||"Cumdump wants to go home..."|