Why are other people letting her ride their horses with the attitude she has? I don't blame you for saying no, she sound unsafe as well as a nightmare.
Of course there is another sort of Arab owner who is possibly nearly as nuts - turns out her ridiculously fit, barefoot Arab in all weather until it grows a coat that makes people ask where she got a Welsh A so big, rides in all weather in a synthetic saddle and an outrageously colourful...