That's a letter of a child. Nothing special for a such age, children write what they think and see just at the moment.
Yes, very true. Anybody who has marked or just read some school children's essays knows these abrupt leaps of thought very well. And they don't even write "And by the way....". That's why they must be taught "text binding" or whatever it is called in English.
BTW (oh, I'm sooo grown-up) one can interpret this nonsensical little message in a rather tragic way considering her future: She was pretty like the roses, married a handsome prince and embarked upon a rosy imperial existence, but the thin, fragile roses of romance won't feed your (spiritual) hunger..... Heavy, dirty, grim beets, that's what's (spiritual) nourishment.
Now who is going to adopt this as their I♥EllaVonHessen4Ever signature line: Es giebt weiße und rothe Rüben. Rüben sind anders wie Rosen, Rosen kann man nicht essen.