You could use names like 'Girls' Secret', 'Ladies' Private Tales', 'Feminine Folklore'.
Well, there are quite a few options. For example, 'The Girls' Hush - Hush', which implies secrecy. Another one could be 'Female - Only Fables', as it gives a sense of stories that are only for girls. Also, 'Girls' Privy Pages' can be a great name, where 'privy' means private, so it clearly indicates that these are private stories for girls.
Some names could be 'Secret Sisters', 'Girls' Gossips', 'Feminine Folios'.
Some really cute names could be 'Twinkle - Toes Tales'. The 'twinkle - toes' is a cute and girly concept, and when combined with 'tales' it makes for a great name for a girl - only private story. Another option is 'Sunshine Secrets', which has a positive and cute vibe. And 'Flower - Friend Fables' is also a lovely name. Flowers are often associated with girls, and 'fables' gives the sense of a story, while 'friend' makes it seem more exclusive among girls.
Some nice names could be Lily, which represents purity and beauty. Another option is Sophia, meaning wisdom. Also, Ava, which has a modern and sweet feel.
Well, you could go for something like 'Ella's Intimate Tales', which gives a sense of personal stories. Or perhaps 'Sophia's Secluded Stories' that implies a private collection of experiences. Another option might be 'Olivia's Confidential Chronicles' as it sounds like a private account of a girl named Olivia.
Think about the girl's personality. If she's dreamy, something like 'Stella's Dream Diaries' could work.
Butterfly Bunch. Butterflies are often associated with beauty and transformation, just like how girls grow and change.
Names like 'Girl Gang Tales', 'Chick Chat Chronicles', and 'Missy Musings' can be great.
Friendship's Hidden Hideout. This name shows that the private story is a hidden place where the secrets and special moments of your friendship are stored, away from the rest of the world.
You can choose based on the personality you want to give the girl in the story. For example, if she's strong - go for something like Brianna. If she's shy, maybe a name like Violet would work.