Adult fiction from around 2007 - woman is grieving her male friend that died in an accident. It’s later revealed she slept with him before he left and offered to skip the trip to stay with her, adding to her guilt

hello, please help me find this book! I read it in 2007. adult fiction. the main character is a young woman who is grieving the death of her male friend. he died in an accident (I want to say mountain hiking but I could be wrong.) her loved ones are confused by her level of grief until she reveals she slept with him the night before he left for his trip. he offered to stay with her but she encouraged him to go and now feels guilt. she sees him in her room, but smaller and nude. he does not appear as a ghost, she can’t interact with him. the story begins after his death.

i think the author is an Asian woman and I think the main character is also Asian but I might be wrong. I also believe the story is set in America.