I think that too, Yoosun gonna leave Hyewon alone and locked up for a while until the investigations on Suh family ends, but it have been a while since Hyewon bloomed, so I think she gonna bloom soon...
I hope Dohwa finds her soon as possible and see that she doesn't want to run away anymore, but she couldn't because Yoosun locked her.
No, if a flower maiden is killed, OR taken before she blooms for the first time, the poison spreads and kills everyone. BUT if a flower maiden blooms and is unattended for the 7 days of her bloom, she dies as if in the full bloom, not spreading. That's why Hyewon threatened dohwa saying that if she spoke the lotus maiden (dohwa's friend) would accidentally be alone during her bloom...
I don't think Hyewon and Dohwa bloom on same day, that happened once because Hyewon slept with Dohwa, If a flower maiden have sex with other woman she bloom a bit, like Yunhwa and Yoosun that time, she just had one flower on her feet, just like Hyewon on her back.
And Yoosun said that Dohwa blooms one day before Hyewon.
If you notice, Hyewon wasn't in pain because of that bloom, because her bloom was not like "that" bloom got it? xD
I dont know if you understand, my english is not so good :c
A flower maiden would be sick for 3 days if she doesn't engage sexual activies, and would die within a year, but don't kills everyone on MG.
She just do that if she is been killed or kills herself, or else that redhead flower maiden would killed everyone on MG when she died because had not sex with anyone during her bloom.

There won't be anymore YoosunxHyewon blooming. If Yoosun founds Hyewon blooming, I think she won't help her anymore.
~But Dohwa can~