I have a few tips for you!
First, if she is using training wheels, that takes the balancing factor out of the equation. So, you have to work on peddling and steering. First, place her foot on the pedals so that the balls of her feet are touching/pushing down. This is not her toes or the heel, or even the middle - it's the area right below the toes and above the arch. This is where she'll get the power and thus the rhythm to keep going. Have her push down on one foot and then the other. (Putting the pedal in the highest position helps for the first foot to push down.) Then have her look up, reminding her to keep her chin up and looking straight ahead. Turning her head, looking down, backwards, etc. will cause her to get a bit off balanced, thus stopping her rhythm. Try getting in FRONT of her and have her ride to you (as you are walking backwards). Encourage her to keep looking at you while pedaling. Try to do this on a long straight road/strip of grass, etc. This may mean you need to get to a park or vacant parking lot so you can practice large stretches at a time.
Once you have her riding using pedals, and she/you are ready for riding without training wheels, I found the greatest strategy!!!! I actually saw it on youtube and watched a couple videos. Lower the seat all the way down so she can easily touch the ground with her feet. Take OFF the pedals. Have her "walk" the bike while sitting on the seat. Then have her begin gliding it. Then have her glide it down a very small hill to get some momentum. Eventually she will begin feeling more comfortable with the balance and can glide and steer. After she gets the hang of balancing it, put the pedals back on (after a day or so) and she'll be amazed that she can probably ride a bike without training wheels. This method is amazingly fast and anyone that I've recommended it to has their children riding a 2-wheeler in a matter or a couple days. Check out youtube for some videos!!!
Best wishes!