Teething

Aidena was found by Flambo and some of his buddies

and because of the royal gem on her head Flambo brought Aidena back, where Flame Princess agreed to take care of the infant until her parents claimed her, sympathizing with the baby, given her father left her to die in the forest if not for PB

And when Flame Princess started to realize it may be a while until her parents stood up she called Princess Bubblegum for advice, and she skipped a very big detail