Hi Chloe,
Thank you for checking out The Baby Sleep Site! I’m sorry to hear you’ve been dealing with split nights for so long! The most common reason for a long period of awake time at this age is some kind of scheduling issue. It may be that your daughter still needs two naps and is using the early bedtime as a second “nap.” You may want to check out our toddler bedtime chart for more information on age-appropriate bedtime here: https://www.babysleepsite.com/baby-sleep-needs/baby-toddler-bedtime-chart/
And we also have an article on what nap transitions look like here: https://www.babysleepsite.com/baby-naps-2/how-to-manage-baby-toddler-nap-transitions/

If you continue to have trouble with this, please have a look at our personalized sleep consultations here: https://www.babysleepsite.com/baby-toddler-sleep-consulting-services/
A consultant can look at your daughter’s whole schedule, bedtime routine, and sleep history and help you get back on the right track.
Please let us know if you have any questions – good luck!