Analyze the details of the following case and post a response to the question.

Glenn owns a ranch that has a horse who is old and only likes to be ridden by children. The horse has not been ridden by anyone in over a year and is fresh. Donna sees the horse and immediately takes a liking to it. She wants to buy the horse for her granddaughter, but first asks if she can ride the horse. Glenn warns her verbally that the horse does not like adults and will likely buck and bunny hop. He also tells her that the horse has not been ridden in over a year.

Donna says "I have been riding horses for over thirty years and I can break this horse." Glenn then makes Donna sign a waiver where she acknowledges that horseback riding is an inherently dangerous activity. Donna rides the horse and it bucks her off and kicks her in the back. She suffers serious damages. Does Donna have any viable claims against Glenn? What defenses would Glenn have against Donna?