Based off this song: https://youtu.be/WX13s_H8X5c

Gaia didn't get the same amount of attention from her mother as her brothers did. This was mostly due to the fact that she discovered her powers last, so throughout most of her life her parents thought she was completely mortal like her father. Her mother was a time guardian and the longer she stayed with her family, her powers would fade which would lead to her slowly dying. So when Gaia finally did discover her powers. Her mother was too weak to give her a necklace or train her like what she did for her sons. After returning to her original realm Gaia was left with mixed feelings about her mom. 

She holds no resentment towards her brothers however. Instead she tries to support them just like their mom would have done !