Welcome! I used to have a mare that bucked, too. She would go down to her knees she was so intent on it lol. All I did was ride ride ride her and spend time with her that way. Get her mind off of it but squeezing her on with your legs and kissing to her, or give her a firm reminder with your heel. Also, turning her into a circle(one rein stop) can make her quit that. But remember, if you do that, make sure that you don't release your rein until she gives to you(moves her nose in and stops moving) Pull into your hip when you do this. It works, lol!!
If you don't feel confident enough to work through it on your own, have someone else ride her for you for a while and have them have you work with them to get the feel of it. If they take out the majority of her bucks and teach you how to reprimand her when she tries again, that might make you feel more confident. Dealing with a bucker isnt fun for beginners or people who havent had experience with it...been there, done that. But she sounds like a great horse. Does she just buck when she's scared? Or does she have a bad tack fit? Teeth? My one mare used to buck because of having stiff joints and bad teeth; once she had more time on her in the "warm up" ring had her teeth done she has been a great horse. Just keep trying, don't give up!