I'm not sure I understand the issue. She says she would be okay with you having another girlfriend, but you don't want one, you want to spend more time with her. Is she not getting that or does she not want to? It seems like there might be an imbalance of interest in each other or perhaps time for each other. You don't have to have another girlfriend as far as I see it. You could just have more friends. It sounds like she could pay more attention to your need for more time too.