I need tips on riding a green horse?

Okay, Ive had this horse for three years now, she is four. She is half quarter and half paint. I have done ground work everysince i got her, and she is definitely ready to start riding. I sent her off to my uncles for a month, because thats what he does, trains horses. And when he got on her, he was like this horse is broke, what did you do? And i was like ive just done a ton of ground work with her, and he was like well shes broke. green broke, but broke. And so he trained with her for about a month, and she finally bucked. And he called me and told me that he didnt want me on her because she is dangerous. He said he has been riding horses all of his life, and training them and he hasnt ever had one buck like that. And he admitted that it scared him. Now shes back at my house, and its been about five months since. I really want to ride her, but i remember what he said. What do yall think?