I don't recall Helen being aggressive towards Adam/Anthony. She seemed very sweet person. Crushed when she found out about his affair (like we see in the beginning a woman literally crushing a spider), so at the end when he decides to go out again she knows what's going to happen and is afraid to be hurt again.
In our dreams, our subconscious mind gives us messages. Points us to what is wrong, what we fear and what needs to be fixed. That dream will repeat itself as long as it takes, until we understand what it means and do what must be done. Obviously, in this case the recurring "dream" is the spider.
At the end of the movie Anthony looked like he'd decided to make things work with his wife. At least that's how I saw it. Didn't take long, though and when he got the key, he was already going back to his unfaithful ways. Giant spider shows up the very next moment.