I'm not going to touch anything serious, just mine thoughts
That's it, I hope nobody have done this before me.
Text may contain mistakes because English is not my native language.
Poem "A dream" (number 8)
You can try to connect the text to main characters, but... meh. Four main girls may be the four friends, and person in a dream - protagonist or some other character.
However, thing that mentioned in poem can really happen to you. It's because brain works faster when we sleep, and when loud noise wakes us from outside, we sometimes can stay in sleep for few minutes, and while your brain collects information about the noise, your dream starts to change and often focuses around this noise.
So when person in the poem heard laughter, her brain quickly changed the dream.
(the sentence about nails worries me, but I can't think about anything)
Poem "A dream" (number 11)
The most interesting line here is the last one - "My lungs were already getting tired."
The irony here is that your lungs can't "get tired" in a dream. You can't feel your inner organs at all, because usually we feel only the pain when organ is damaged or something. In a dream you can't feel pain.
Also, if you're in the water in a dream, you can breath.
Although, one time I had a dream when I have drowned, and after I "died" I woke up immedantly. Later I have discovered that some people had the same dreams. It can be caused by health problems (most likely heart or lungs problems).
So maybe it's not a dream. We have three variations
1) I think it's a memory of some kind. Maybe past-life thing, though I don't belive in it, but we are talking about a VN, so
2) The person in reality suffers from real heart/lungs problems.
3) It's a reality and person is mentally ill and they keep thinking that it's a dream.
(I think it can be possibly connected to libitina theory, but it's only a possibility.)