2:36 - Original line of Yumeko was "Nechoruna". Based on what I could find from japanese touhou boards and just google in general, it seems to be something alone of the lines of erotic touhou stories. At least I think. So Yumeko might be saying that something naughty was happening in the dark bubble or that she was going to write a fan fic about Meirin and Rumia.
5:03 Original line by Cirno was "Futomashiku dekitainda." Based on what a Touhou wiki told me about "Futomashi", its a word used for Letty to basically say she's got a sexy body. Basically a backwards word used from the other meme that says Letty is fat(Debu).