Every time she tries to get on your shoulder block her with your other arm and then station her somewhere else. Try again. If she heads for the shoulder again, repeat. She's intelligent...if you do that EVERY SINGLE TIME she heads for the shoulder, she'll catch on. I'm not saying she still won't try but if you are consistent the attempts will become fewer and farther between. Alllow her to do it once and she will backslide. Here my shoulder is by invitation only and honestly my birds are not comfortable there any longer because they have been taught that it's not a hang out spot.