I have asked for Emmas help but she refuses to take down Mario. I even tried doing it on another save but the same happened. On both saves i had sex with her ten times or more.
The most probable thing that I'm expecting happened is you selected: "do you know your ___ fucks a lot of sluts" during the second sex scene with Emma at the sauna, which is the share choice. And since you had told Mario you wouldnt help him, and Sofia is expecting Emma to help then the quest is basically in Limbo.
The quest will have some changes later about this choices, to prevent this kinds of "limbo" situations from happening. Another example would be to not share Emma but tell Mario about Sofia (this is another limbo state)