well with her she is a little different. You can't tell if she wants another one. So what I do is keep throwing one in there with her if she takes it then I will put another one in there after she has re-aligned her jaw. When she goes the opposite way from the mouse it means she is pretty much done so I take it out and put it back in my mouse cage.
That's what I do with my mouser girl also. I can get her to take a small ray every couple months or so. I'm planning on trying to switch her soon.