Yes, this is a phase and this is a teaching moment. This is a great time to get your daughter information on boundaries. She is spending her time felling responsible for someone else's well-being and that is only the path of frustration and co-dependency.
It sounds like your daughter can be empathic and sensitive to others. This can be a valuable tool in life however, when we don't understand how to actually use this we have a tendency to be misguided and think that we are helping someone else through our processing the emotions for them.
Your daughter could use some understanding of how to separate and allow each person to have their own journey. It would help her to understand that as much as we would like to make life easy and hurt-free for other people, this is not possible. We each have our own journey through life and need to experience everything we are experiencing.
Also, there is a difference between support and fixing. Support is about listening, sharing, and caring. Fixing is trying to make it all better. The reality is that the only way that it can ever be better for someone else is for them to work on their own inner healing.