A person only has so much emotional capacity. If she is already struggling to meet the needs of the people in her life, why in the world is she dating at such a high volume? I understand wanting to look for a sub, but does that mean she needs to go out with a different person every week? That seems a bit excessive to me. Especially when she knows that at least one of her partners is really struggling with feeling neglected.
To me, it sounds very simple - she's stretching herself too thin, regardless of her good intentions. Attempting to be supportive and understanding and actually succeeding at being supportive and understanding are two very different things.