I can appreciate your predicament.
Jo*Mar has mentioned some great ideas!
Just a couple of ideas as I read
How about an old fashioned (loud) hand bell at her bedside?
(Teachers used to use them in class.)
How about one of the many designs for wireless doorbells available at many home improvement stores? If the button is easy to push, it could be mounted in various ways, either secured near her or creatively secured to her person/her clothing?
(There are so many types of these, with so many types of buttons. Most buttons are mounted on display for trial at the store. They are totally wireless and most of the doorbells are quite loud!
Hmmmm... I will have to keep thinking!
Good luck with this!