Haven't heard of any reports of those in these parts.
I think it's a matter of being responsible when you drive anything like an ATV or snowmobile or motorcyle or jet ski....
Some people push the fast factor and loose control and therein lies the danger. Many people enjoy these recreational sports without any incidents and yet, even experience riders have been known to have accidents some where they were able to walk away from it and some where they were not able to walk away.
I rode as a rider on the back of one one time with a friend...he tore through his property at a fast pace and scared the boogers out of me going through trees and such but he knew his property where as I did not and would have proceeded with more caution...what he DIDN'T expect was one of his horses to be standing in the middle of the lane (who had accidently gotten out) making him have to veer to the right sharply and we tipped it some but instinctively I put my foot down to prevent it...only to be run over by the back wheel...leaving a nasty scrape on my toe since I was wearing my tevas (sandals) probably worthy of an ER visit but I didn't go...instead I just limped and hurt like heck for a number of days...weeks...
Lesson...never let crazy friends drive and you never know when a horse might get loose.
Often you hear of snowmobile accidents involving such things such as a barbed wire fence that wasn't very visible if it was dusk or dark or just the simple fact that it's hard to control when you are going at a rate of speed and say the ice caught you off gaurd and flipped you...same with an ATV....gravel or brush depending on where someone ATV's can become a slidding/tipping factor and must be considered.
At much as they can pose a danger...so can the day she is old enough to drive a car, dad. But I assume you will trust her to make the decision to drive responsibly and know if an accident happens...that's what it is...an accident and all must be forgiven. We all take that risk every day when driving.
Sometimes these things are short lived so I'd look for a used one that is still in good shape. I have a daughter who is not athletic but she sees the rest of the neighborhood over by my mom riding those electric scooters. I was afraid for her...thought she'd fall and have to get stitches...get a concusion...break an arm...I got her one because I know that's what she wanted the most for her birthday. She tried it and was scared and would jump off and dump it. This year her balance is better. She's not where other kids are who are her age or even younger when it comes to things like this but I don't want to deny her. She may play for hours with a silly little beany baby stuffed animal and spent a whole 20 minutes trying to ride that thing but she tried and she'll keep trying and one of these days she'll get the hang of it. I believe in her. I also trust that she will not abuse it and ride it irresponsibley like I've seen some kids swerving in parking lots and not paying much attention to traffic when they go beyond the bike path part when they are heading home.
I have another daughter who is 5 and has almost no fear... I will have to believe the things I teach her and tell her about the ways of the world and life that she will abide by them and when she does...drive...or what have you...that she will know that is not the time to push limits and boundries but to follow the laws of the road for her safety and the safety of others. I remember seeing the litttle dirt motorbike racers one time at the 4-H fair and thinking...oh boy, if Ava see's that, she's gonna wanna do that. Same with muttin bustin and rodeo stuff...she sees it... she's gonna wanna do it.
I can't say that I won't worry...because I will....but I want them to live and experiance life and if financially you can make it happen then I wouldn't hinder it... I would let them spread thier wings and then pray earnestly for thier saftey. If they disobey the rules set by you...then take it away and give her another chance...disobeys again....sell it. Like I said...it could be short lived or it could be like my daughter and her electric scooter and be collecting dust in the garage.
And if there's someone you know that's older and more experienced...set it up so she can take lessons on the rules of running one of those things. Make it mandetory.... 3-5 sessions of an hour 1/2 long.
It's like me taking a sailboating class before I got a sailboat....but she may need the ATV for her sessions if the older more experianced person doesn't have an extra one her size...