If she even gets the MC involved last time she called for help MC sent her straight to VM, which would make her question his reliability. She then sees what they did to Riona, which was a slight eye opener to what happens to people who don't belong in that world,before going on to distance herself from MC telling him she doeznt want him in that world.
The games not exactly set up to have the MC come in like a knight in shing armour, nor does he need to be, not every story needs resolving with the MCs input
In this case in particular the game does actually. It's not that Quinn is going to ask for help, she probably won't (or maybe will).
It's the MC that will notice that she needs help and will run to her, but only if he is her route. She has trusted him with life story, he knows who she is and can, despite of all that, still choose to understand and be with her.
The more I play Quinn's route, the more I'm certain that DPC heard the song 'Time to Rise' before making Quinn and actually made a character that was that song. MC is one of the lights Quinn found in her journey and it's the last one she has. She lost everything, so regardless of what she wants, if us the players want to be with her, we most definitely can.