MarrikBroom

Considering the last panel, I'm hoping the mention of Jerry is enough to calm Susan down or at least make her more open minded about all of this, she can still hate the idea that her father had been cheating on her mom for years, but hopefully she will at least acknowledge that Nanase and Ellen aren't just making any of this up.
If Nanase hadn't done more research, they would have ended up going into this with "So our friend Diane, who looks at sounds a lot like you, born 20 minutes before you, and was attacked by a vampire for having the same affinity as you. Also she was protected by who we believe was Jerry at the New Years party as a favour to her sister. She's adopted though, so we think it might be possible that you're adopted too?"
I think going into this discussion with only assumptions would have been worse.
 

ASame... given I've seen my own family isn't great finding anything positive to hang onto mean a lot. The fact Susan already is having to protect what good she can is somewhat telling, and her reaction is... I totally empathize with what she's gone through.

I have to take Nanase's position: You can't skip warning people about threats to their lives or their relative's lives just because the warning is traumatic, and Diane is nowhere near corrupt enough to decide her survival doesn't matter compared to antagonizing Susan.
I do agree that with 20-20 hindsight they should have gotten an intermediary and done less intrusive research, but until after the fact there was no way to know that wouldn't be even worse.

This may be the most painful page of EGS that I have read in quite a while. I don't think I have seen anything even near it since the time Tedd acknowledged Mr. Verres' transphobia.
It is clear that Susan has held a mental image of her father close in which she tried to preserve at least some sort of person worthy of love. It would be easier to think of him as someone who started with good intentions but stumbled into a bad mistake. Being brought face to face with the possibility that not even this much was true... yes, anger and denial are two of the first steps. Having it all intermixed with her immensely traumatic experience with the vampire back in France would not make it any better, to put it mildly.
I am torn. Nanase unquestionably meant well. But I am starting to think that she would have done better to think this more carefully through. Even so, I am doing this from hindsight so I am not precisely in a position to criticise her. Her intentions are obviously good and based on the fact that not only is Diane in danger, she also deserves to know of her half-sister's existence... and that Susan deserves to know the truth as well.
The problem with that is that while truth indeed has the power to set you free, it can also open old wounds and do grave harm. It is for that very reason that Ellen rejected the notion of telling Tedd what they had learned about his mother. This situation is of similar complexity and may well reopen old wounds for Susan... and possibly even make them worse.

http://www.egscomics.com/index.php?id=2271
Accidentally ominous Tedd is ominous.