Regarding the (first) "odd" translation, it's not actually 本 but 体
自然体でって言ってたのに
Basically, this translates to "even though they were told to act natural"
It's basically additional commentary on the speech bubble where she mentions that they're overdoing the act.
Edit: Regarding the 2nd "odd" translation,
Here's an article on the expression for throwing up sugar.
It's primarily used to describe anime type stuff. It expresses how some characters are so lovey dovey that one feels like they're throwing up sugar. (Because they're too "sweet.") In other words, "So sweet it's like throwing up sugar."
Oh, also, it's not "I want to throw up sugar" but "I feel like I might throw up sugar." 砂糖吐きそう (the そう is used for things that one thinks will happen in this case)
Edit 2:
Since I was curious, I took a look at the last line in the extra panel as well.
今一瞬すごいバラの香りが
The すごい in this case doesn't really mean many. It's just an expression similar to "very/super." Maybe something like, "Just now, for just a moment, [there was] a super strong rose smell."
Edit 3:
"Yours is specially many"
特別の大盛りですよ
大盛 is a large serving. I dunno, translator probably knew what it was but just phrased it a bit odd. "[It's a] special large serving!" the よ is sort of like emphasis. Maybe kinda like, "y'know?" or something. It can be used when informing someone or something.
I'm guessing this is the correct tag for the person that wrote the comments at the end of the chapter:
@Kakkoiikun