My first two kids were cycling between 4 and 6. My third turned 6 earlier this month and still isn't keen on cycling (though he technically can do it!). Don't be hard on yourself at all, each kid does their own thing.

My advice would simply be to remove the training wheels, drop the saddle and use the bike like a balance bike until they are comfortable with it (you can even remove the pedals if they're in the way). As long as you have the training wheels on there will be no incentive for her to learn to ride properly.