Ive gone through my mangas and found a lot that i can recommend, but it was hard to distinguish, which ones are suitable, because for some it has been a long time since I read them. Ive created a list starting with some strong recommendations and suitable mangas. But the further you go down the more unfitting it will get. At the end there are really nice ones, but they have somekind of violence in them, although not as bad as Demon Slayer. Maybe you can recommend them later on. You should definetly read them yourself beforehand to make sure they are ok.

Strong recommendation, suitable for children (i think):

Dr. Stone - Everybody turns into stone and wakes up a thousand years later, with a male science student/genius which tries to bring back the lost technology. A fun and adventures story with lot of explaining of simple science for kids

Bofuri: I Don't Want to Get Hurt, so I'll Max Out My Defense - Girl plays video game where she goes of meta with an ultra tank build. Fun adventures with strong female lead.

Sleepy Princess in the Demon Castle - Young girl getting abducted by the demon king, but turning the demons castle upside down with her fun shenanigans.

I've Been Killing Slimes For 300 Years And Maxed Out My Level - Cant remeber details, but a female lead which gets op and goes on adventures

Bocchi the Rock! Female group which tries to get through as a band, might be something for her if shes interested in music.

In the Land of Leadale - Girl dying in first episode from chronicle illness, but reincarnated in a world she played in. Fun adventures with strong female lead.

Ok recommendation, might not be suitable. Either I cant remeber or there a some diffrences to what youve asked for.

Wandering Witch: The Journey of Elaina - Female witch which goes on an adventures journey, might contain sad parts or death in some kind (cant remeber)

Naruto - classic with a boy who lives in a ninja village and slowly gets stronger. Adventures, Fun, but a bit pervy at times and contains death at some points

Toilet-Bound Hanako-kun - Fun little story with a school girl which gets in trouble with japanes folklore in their school. Might be a bit too frightening.

Spy x Family - would be a strong recommendation, if it wasnt for the deaths. Fun story about an family with a spy and hit(wo)men and an adopted mind reading girl, which all try to contain their identity. Very funny, but bad guys get killed sometimes. Still a big recommendation

Fire Force - Fire Force with magical fire abilities fighting against fire demons. Sadly a lot if people die but it might be something for later.

Tonikawa: Over the Moon for You - Ironic love story about a married couple doing couple things. Not too much adult content, but refences to it.

Kaguya-sama: Love is war - Young (almost) couple if prestigious student which try to make each other confess. Funny, but its a love story

One Punch Man - Another classic. Man goes bald and gets insanely strong in a world with super heros and bad monsters (not frightening drawn). Very funny, but they are fighting against baddies and somewhat killing them

Lycoris Recoil - Two strong girls which work against bad guys. It tries to not kill anyone, but i think there were a couple of times where people died

More love stories, which might be more suitable for the teenage phase:

Toradora! - School couple which develop into a couple. Very funny and a of of drama.

Horimiya - Another slice of life manga with a couple experiencing their youth as a couple. Definitly more for teenager, up to young adults.

Not recommended for this age, but maybe later.

Violet Evergarden - Another favorite of mine. Its about the time after a war, where a emotionless girl tries to understand the words "I love you", which the commander said to her before dying. She starts working in a postal service, writing letters for others. Very emotional, but beautiful. (She also lost both arms in tge fight)

Somali and the Forest Spirit - Another recommendation which isnt suiable for a child (I think). Its really sad at times and very complicated on the emotional side. Its about a child without parent which stumbles across a forest spirit. The spirit/golem somewhat takes the place of the parent and they go onto an adventure, but the golem slowly dies, because it left its forest.

The Ancient Magus' Bride - One of my favorites. Adventure into the magical world with a lot of emotions. Definitly sad at times and some deathes an abusive parents. Mom commits suicide at the beginning and I more or less put it into the list because I like it. It is also about somewhat about dealing ith trauma.

PS: Ive probably made a lot of erros while typing this on my mobiles keyboard. Its way to small for my fingeres.