I think it's related to her chi...like in that ch if you see clearly ( I might be wrong tho) that while she's bleeding she infuses her chi with it so the leaf burns(?). So I think she can do all the blood poison thing if she wishes while infusing her chi with it. She has been a master of chi from the beginning of the story so that's why I think the story skipped the part about her being worried about kiss, sex and having kids and stuffs
I think it's related to her chi...like in that ch if you see clearly ( I might be wrong tho) that while she's bleeding she infuses her chi with it so the leaf burns(?). So I think she can do all the blood poison thing if she wishes while infusing her chi with it. She has been a master of chi from the beginning of the story so that's why I think the story skipped the part about her being worried about kiss, sex and having kids and stuffs. It can be related to her emotions too, like if she was too stimulated the poison would activate, but that's also just my hunch, it can't be true as we see her crying once and her tears clearly drop on the ml, but nothing significant happened, and not to mention they kissed...This is either a huge plot hole or just a trivial matter (as it relates to her chi) so the story skipped it.

The only gripe I have with this story is that I thought Haewon’s entire body becoming poison was going to be a WAY bigger plot point. Like I was so excited to maybe see her wipe out a whole group of people using just her breath or sweat or something in like a “gotcha” moment.