Why is my daughter not sleeping through the night anymore?
If she is a baby, especially around 4-6 months old, she might be hungry and ready for solid foods or a more varied diet with more protiens in the evenings.
Teething pain can also wake babies up at night even if they don't notice it during the day. My pediatrician recommended to us giving a dose of ibprofen immediately before bed every night from when our son first started teething untill he had cut most of his teeth,
Toddlers or pre-schoolers might just be ready to give up some nap time. I found that when my boys where still on a two nap schedule elimatling the afternoon nap and then slowly pushing back the morning nap into the afternoon seemed to work best. That way when we first changed they were the most sleeply in the evenings.
The most difficult reason your daughter might be getting up is that she is nervous about something. My 3-year-old started getting up and wanting to sleep with us when my baby bump started showing over the summer. It got even worse when his older brother started Kindergarten in August. Because this is very uncharacteristic of him we have been generally sympathetic of him with this. We encorage him to go back to his bed, but will let him sleep on the floor if he wants to. We are counting on this passing after the baby is born next week and he has some time to adjust to all the changes.
How old is she? My little boy was fantastic by 6 weeks old he was probably sleeping through the night 4-5 nights a week, and I understand I was extremely lucky (hopefully lucky again for the next one that will be here in a little under 2 weeks).
But, when he got a little older he would wake up and its hard doing tough love (controlled crying) they call it something different now I believe. But I think when he had teeth coming through he would wake and most importantly... my mum said to me she didn't believe he needed a day sleep anymore - so eventually this was dropped out, sometimes he would need a day sleep but since then he hasn't really woken up unless his routine is interrupted like if we go away for the weekend. I am not a strict 'routine keeper' but something different this time last year would cause him to wake.