Dd might be a little young to learn, but if she is quite tall and strong she will manage it. DD1 learnt when she was 4yrs, DD2 when she was 6yrs, we tried both at different times and when they were ready, they picked up in a day. So if it is taking too long they are probably not ready.
For us, we went to a wide open short green grassy space that was completely flat and wide. We had the bike checked so the child could firmly put their feet FLAT on the ground, this is important for feelings of safety for the child and their fingers could completely cover the brake. Next you need to run along with your hand on the child's back, one hand on the handle bars balancing them whilst they peddle in straight lines.
Do not attempt to go to the left or right or turn at this stage.
Being on grass it is harder to cycle, but definitely safer and will not put your child off when they fall off (which they will on numerous occasions) once they conquer the grass they will find it so easy to transition to the smooth surface of pavements and roads.
If you practice with your child running up and down and then gently remove your hand from the handle bars. Supporting by back afterwards.
Once this is achieved it is relatively easy to remove your hand from the back and they should be off. With lots of cheering and applause!
Then they can practice turning the bike and then braking. I would ensure they were completely confident on grass before moving to pavements etc.
PS Get dh/dp to help, it is very tiring! :)