Jay, if you really want to encourage her, you know the answer. She may end up being an atv kid, but at least she'd be out there doing it and feeling part of it. She may just be testing the waters to tell you what she really wants, so I wouldn't rush into buying it for her.
One of the kids we ride with is on an LT80. She wants two wheels, but when we ask her if she'd ride certain trails with us, the answer is "no". She was busy telling me last time that they were selling her quad & getting her a bike, so I asked her again, would you ride that trail. "No" was her reply, so I told her that her parents won't be buying her a bike. She's thinking she can keep her quad & get a bike (which would be the ideal solution), but as she's the youngest of three kids, that won't be happening. We may see her on two wheels one day, but not yet. Her parents would rather her ride everywhere with us than give up. She does enjoy herself when she gets to ride a bike, but just isn't prepared to ride everywhere - she's starting to feel she's missing out (she's not).
Seriously though, do see how this stage progresses with your daughter & if in a month she's still keen to ride (with trainer wheels), give it a go. Or give it a go anyway & see what happens. If you point blank refuse, I'd guess that she'd definitely never end up on two wheels.
Good luck & don't forget to post pics of her on her four wheels :)