Translation from here

Also worth noting is that, aside from being unexpectedly verbose, Fran is writing only in hiragana. This is something generally associated with children and forced-cutesy idol types acting like children, since children don't know kanji, and kanji is rather important in figuring out exactly which words you're going for in Japanese. (There are a ton of words that are spelled the same in hiragana, so it's a guessing game based on context, and they don't even use spaces between the words.)

Basically, it's a form of gap moe Gudako's reacting to.

NWSiaCB said:

Also worth noting is that, aside from being unexpectedly verbose, Fran is writing only in hiragana. This is something generally associated with children and forced-cutesy idol types acting like children, since children don't know kanji, and kanji is rather important in figuring out exactly which words you're going for in Japanese. (There are a ton of words that are spelled the same in hiragana, so it's a guessing game based on context, and they don't even use spaces between the words.)

Basically, it's a form of gap moe Gudako's reacting to.

Also makes sense seeing as while Frankenstein is surprisingly smart, her mind is still a bit hindered by having Madness Enhancement