that cheap of a RC will come with a ESC and motor that will not handle 3s.
in fact, even a 2s could overheat the ESC and shorten the life of the motor.
if they die, you can get a traxxas xl5 and a decent motor for around $50.
if you wanted to upgrade the ESC and motor to brushless, youll spend around $100....plus youd have to upgrade the buggy itself to handle the power.
I know the perfect buggy for your girl, the thunder tiger phoenix XB. you can get one on tower hobbies for $200 shipped. it is brushless, lipo ready, tough and handles decent. the radio has a duel rate for the throttle....this means you can adjust the top speed right from the radio.
this buggy is a re-branded team associated B3, which is a older buggy but is known as a decent racer and for being durable (as durable as buggies get anyway)
tbone racing makes a nice front bumper for the TT phoenix that ups the durability a fair bit.
this buggy ive owned and have run 3s. but honestly you will want to buy a $35 2s pack from hobbypartz.com, as a 3s is simply too fast for young kids.
I usually ran 2s, and when my girl wanted to drive I would just turn the throttle duel rate knob on the radio down and hand it to her, knowing it would be slow enough for her to safely drive. it is a good buggy for the money, you wont find a brand name, brushless buggy for less.