Yeah, I agree with everyone. Free feeding's out for her. You're going to have to monitor her intake, and go with strict portion control. I don't think you need to change foods just monitor how much.
Tango could have been free fed his whole life if I hadn't gotten Jazz. He monitored his own intake, eating just enough to satisfy him I guess, because he never overate and he never gained weight once he reached his mature weight. But once Jazz entered the picture (who WILL eat until she bursts) Tango became very interested in the Merrick puppy food I was feeding Jazz and started stealing it at every opportunity, gaining a couple of ounces in the process...which doesn't sound like much, but when you've a dog who's only 3 lbs 8 ozs, every ounce counts.
I did portion control with Jazz after about 2-3 weeks because I could see what a pig she is. I rescued her at 11 weeks, and by 13-14 weeks she was eating a very strictly controlled amount, separate from her brother who was on a different food and kept trying to steal hers.
They're both eating Evo now, which makes it easier, but they still try and eat each other's food...don't know why coz they're fed the same thing lol! And Tango's lost that couple of ounces he gained, which is good. Jazz is still gaining, but she's lean and muscular, and I expect her to continue to grow for some time yet.