So, the opening sequence of the trailer saw a rather uncomfortable scene of Helenas terrified sister and her presumed demise at the hands of Derek, and I think most people shunned this off as a scene to create more emotional tension, something Capcom seem to be aiming towards in this game, with the zombified daughter and such. However, I think there is a little more to this scene, and it all comes down to one part of it.
This part is Helenas screaming to take her and not Debra, and Derek ignoring this. While it could be one of those dramatic film moments where a protagonist wants to sacrifice themselves, I think there is a bit more substance to it. If you remember back in the first trailer, Helena said that something was her fault, and what I think is that she previously worked with Derek on perhaps the C-Virus or some of the B.O.Ws such as the new insect-like ones we see. This can be supported when in the second trailer when she says that none of those thing were there previously, indicating she had been wherever they were. Also, the scene began the trailer, so it must be pretty damn important.
So, another day, another theory. I should make a series out of this.