Issues with the daughter of my girlfriend

I'm 27 male, and we have fallen in love with a single mother (28), things are going great, we are going to move in together. I'm the first long term relationship she had since her daughter was born (they have separated with the father very early). I also have a small child, whom I only have custody of part-time. Everyone loves everyone, it's starting to become a family.She is working one month abroad, and for the last week I'm taking care of her daughter during the day. She is 7 years old. We have great time, she seems to be enjoying herself, I like to take care of her, we are bonding.But there is one problem. Even though one on one the daughter is really nice with either me or her mother, if we are all together she seems to be really bothered. She wants attention all the time, interrupts every conversation. She is especially bothered by any displays of affection between her mother and me. If we hold hands or hug, she always has to come and declare her love for her mother and hug her. It seems like she is afraid that the fact that her mom loves me means that she doesn't love her any more. We have tried explaining, doing stuff together, anything we could think of, but the problem persists.Any advice would be appreciated. Did anyone go through something similar? How did it go? via /r/Parenting http://ift.tt/2al9YKb