Absolutely not too late. I've worked with middle aged and older dogs who transfered quite easily to the clicker. For dogs who have been trained traditionally it can take a little longer, as they've generally been taught to be good little soldiers and wait to be told what to do. But it can be done and some of the results are spectacular. For behaviors she absolutely knows (be aware that she may know them at home, but not in a distracting environment) you don't actually need to click. or click all the time. But be sure she really knows your cue (word or hand signal) before you assume that she's rock solid.