I see 3 possibilities:
1- The responsible is Hana. It seems to be the most likely option, because A- she obviously is the one who recorded you; B- The threat actually serves her objectives which are to make Sombra sufffer, knock the MC a peg or 2, and leave her in a perfect position to swoop in and pick up the pieces, so that she can, and I quote: "make it mine"; C- That sinister smile at the end of the sex scene suggests that she is not in a good place, mentally; maybe she is becoming some sort of yandere? That would explain the lack of logic in her actions;
2- The responsible is Sombra. That one doens´t seem logical at all, HOWEVER: A- Blackmail *is* one of the tools of her trade, and B- Like Hana, she seems to be at a loss dealing with the fact that the MC is a genuinely decent person, yet not just some sort of simp to be used, discarded and is, despite herself, falling for the MC. MAYBE she is self-sabotaging, conscious or unconscionally, so that she won´t feel that way?
3- The responsible is someone else entirely: In that case, all gloves are off.