I'm facing more or less the same challenge, but from your partner's perspective. The little girl will be 5 very soon, and behaves more or less in the same manner. She's also crying most of the time. Her mom who I love more than anything in the world, drops her off at preschool in the mornings.
Myself and the little girl get along fabulously most of the time, but she will get moody sometimes, and will get very jealous when myself and her mom show affection towards each other. I really love the child, and don't really know how to handle her when she gets like this.
It has gotten to a point where her mom decided it is time for a time-out in our relationship, and she is putting all her effort and energy into her children. It feels like I'm losing them, and my heart is breaking. I miss them so much!
Any good advice you might have stumbled across will be much appreciated.