I'm sorry this is happening but now is the time to get this worked on, so she does not continue in school and end up labeled permanently as a violent troublemaker. Sorry, but teachers, administrators and other families do label kids, and those labels stick hard and long. It's certain that every family in your school knows already that she broke a child's nose, and whether she did it on purpose or with an accidentally rough swing, the parents are going to be wary of her and will tell their kids to be wary of her. It's unfortunate but true: We all keep up with which kids hurt other kids, and even if we feel sorry for the kids who do the hurting, we also want to keep our own children away from them. Work with her immediately to get her on a better track so this problem can end with this school year.
The phrases that jumped into my mind were "anger management" and "impulse control." She needs the former and needs to learn the latter. You mentioned "she is very very naughty" but didn't give any examples other than punching this other child and "she likes fighting with boys," so it's hard for us to know what "naughty" means -- and punching isn't "naughty," it's violent.
Definitely professional help is the route you need right now, even if it costs, because: First, she may not pay any attention to you telling her to behave differently, because up until now, this is "normal" for her and she's used to rough play and won't understand why you're now saying to stop. Second, if she is at the point of injuring other kids, you need to show the school and other parents she is getting serious help, or eventually you and she could end up in legal trouble, as another person who posted has pointed out. Third, you yourself are framing this problem as "she needs to be more girly" and "she's naughty" and "she's been playing with boys" -- those don't seem to face the real problem here. You also say you're nervous and scared to deal with her school or face her teachers -- which honestly means you need someone to guide you and counsel or even diagnose her.
One more thing -- You didn't mention: Does she understand what she did and that it was wrong? Even if she insists it was an accident, does she take personal responsibility for it anyway? Has she apologized to the child? If she is showing real remorse about what she did and really is upset that she did it because it was wrong -- not just upset because it got her into trouble, but because she knows it was painful to someone else -- that is a good sign and shows she can understand others' feelings. But she still needs to see someone professional. Talk to the school counselor and your pediatrician to get referrals to child psychologists who specialize in anger management or whatever the counselor or doctor think she needs.