Maybe Astrid made them up, but they are not used as names for persons (but for pets and dolls). Pippilotta is not used as a name either. But Madicken (originally a nn for Margareta) is used.
Pelje I don't know of. Do you mean Pelle, an old nn for Per? "Tomte" means either brownie or Father Christmas, not used as a name.
Interesting that Ronja existed as a nn in another language.
"You sought a flower and found a fruit. You sought a spring and found a sea. You sought a woman and found a soul. You are disappointed." "It does not become me to make myself smaller than I am." (Edith Södergran 1891-1923)