@Risamari
-Spoilers for DDLC down Below-
All of the poems can be found on the wiki: Natsuki Yuri.
Two of the few poems I particularly find to be of interest are the beach poems from both Natsuki and Yuri, which they wrote for each other. Natsuki's poem has a clearly romantic style to it. If you are feeling skeptic, you could say that it's purely stylistic and metaphoric, but it is there. Yuri's is less overt, but if you read it with the right frame of mind you could interpret it to be quite suggestive itself.
Another two poems I find interesting are the two cryptic poems each from Natsuki and Yuri in Act II. They get pretty graphic so I won't repeat them here, but they seem to be directly related to each other, particularly the end of Yuri's cryptic poem.
Also from Natsuki is the "cry for help" poem which mentions that "she always wanted to be better friends with Yuri." As well as Amy Likes Spiders, which has the obvious intention referring to Natsuki's like of manga, but if you want to be extremely critical of every detail, the poem could be interpreted to have a second meaning.
As for the in-game dialogue, I don't have access to the game right now for various reasons. The lines I'm referring to are scattered throughout the game, but they're there if you're looking for them. There's one line from Monika specifically about how she can't stop the girls from falling in love with you and it's like they're hardwired to by the game, or something along those lines. This is obviously after she reveals to you that she's been driving them crazy by tampering with the game files. I believe there is also a part in Act 4 (after you delete Monika) that shows Yuri and Natsuki reading together, or something along those lines.
Anyways, sorry I couldn't be more help and post actual dialogue from the game. I'll be able to play it again in a week or so, so if you want me to take some screenshots I could do that then, before school starts back up for me.