The last panel, I don't know if I can sufficiently translate; from what I can tell, it's a play on boke/tsukkomi stuff, but I don't think I can put them into terms that succinctly communicate the dimensions of meaning. If someone wants to take a crack at a fresh and more true translation, go right ahead! I'm always eager to learn.
Additionally, that big bottom-right Sachiko bubble, I'm very shaky on. Requesting a correction.
Updated
MizuSachi BdayMizuki-san!
Sachiko-chan!Happy birthday!Fufu-n.
My cute self and......cutie Mizuki just turned 14!wh......what the heck.*serious jitters*Yup-
Don't hold back on the retorts-Sachiko-chan......Ah, but the number one cutest is myself, you know!You're not holding back at all!Huh? You're really not joking......Sachiko-chan, is it fine for me to get this close?I think it's cute!Ah... but...
Given Mizuki-san's hard work with that kind of behavior......