How to manually manage My music and videos on iTunes

I recently downloaded the latest iTunes and I am having trouble putting songs on my iPhone 3. I use my daughter’s iTunes library and I own iTunes library to put songs on it. The trouble is I Click the “manually manage music and videos” on my daughters iTunes library, put the songs on my iPhone, and then eject it. Then go on my own iTunes library and look at the “manually manage music and videos” button and see that the button is clicked off, hence when I want to put songs on my iPhone they get deleted. I have restarted the computer and nothing works. What is the go? Why does the button click off, and so I can’t put songs from my daughters library and my own (as she has songs I don’t)