It's a little bare bones for someone young, but you could try Anki. It's a generic spaced-repetition app, so you would need to grab a deck of flashcards from the AnkiHub community for your language of choice.

As an adult learner:

For apps, I use Clozemaster and Babbel. Unfortunately Babbel is starting to feel like it's also chasing gamification, but it does have sensible content.

For podcasts and YouTube content, I follow EasyGerman and Coffee Break German, and both are part of larger brands for other languages:

https://www.easy-languages.org/our-languages

https://coffeebreakacademy.com/

For kids… what about kids books in the target language?

Not knowing what language she’s learning, it’s a bit tough to say. Many have an app with lots of reading material with audio and assistance tracking learned words, tap to dictionary lookup, etc. It’s a pretty good category and a lot of kids enjoy them.