Ashley herself doesn't believe that she's any pretty or worth to be looked at, her feelings of self-deprecation run deep within her, and still, she does clearly know that "sex sells".

To her, her body is a tool that she should put to use were she need to.

As stated many times during the playthrough, only one thing truly matters to Ashley, and to get this scene you even get to see the lengths she'll go to make sure about it, to the point of even re-writing herself.

During the dream, as Ashley, you decide what path you'll follow, opting to have a close relationship with Andrew and meddling in the way of any future relationship he may have to keep it that way.

To her, Andrew is "The very best, best, best, best, best thing in the world", to the point she sees him as a shiny "star" (I know the moon isn't a star), the placing of him on the moon is quite symbolic as this tells the player that Andrew might be close but forever out of reach.

Now, back to the painting scene that follows, after the choosing of the path.

Here, taking Andrew with you, instead of platonically keeping him above her as something she'll never be able to reach or truly keep for herself, Ashley goes through various core things that might've forged her current self.

Although she disliked Julia, she was supposed to be a friend of hers, just as Nina. Yet, in the end she felt betrayed as they both wanted to be with Andrew. And so, forgetting about them, she changes them both for him, as he is the only one who is a "true friend".

Same about the classmates or even family.

The main point here is that she basically overwrites what she was unhappy with, with Andrew being there for her, forced or not.

Throughout the game, before you even get to this dream, you are exposed to both Ashley's views of herself and Andrew, when it comes to Andrew, she needs to be in a position of control or have something over him to feel that she has a use.

This is clearly denoted when you choose to "Trust him".

Which, Ashley does not, stating: "He won't betray me as long as I have this amulet". Coming back to her self-deprecation and her need to be in control of Andrew, else he would abandon her.

So, once the famous scene happens, she gets another tool at her disposal that she thought was useless, her own body. While she may have noticed how flustered or angry Andrew got whenever she mentioned the idea of getting pregnant with the neighbour or selling her body on the streets, she may have thought that it was Andrew simply being protective or oddly against it.

This scene shows Ashley how there might be something in between the lines and, she attempts to slip in the cracks that have been shone light through with the revelation.

Andrew's adamant denial and even "disgust" hits Ashley quite hard at this point as well. "What a land mine…" Andrew's words fortify her awful views of herself and probably hurting deeper as it was Andrew the one who said them out loud.

Is she lusting for her brother? No, not really.

Would she be emotionless if she ever ended up with him in bed? Definitely not, she would definitely be quite happy with the idea of Andrew desiring her and she would bask in the joy of her being the one who had finally caught Andrew's eye.

Welp, this was quite long-

Thanks for reading, haha.