Although Liam is heaps younger than Liana, when we moved him to a bed, we got into a really big overtired cycle & he was sleeping about 10hours/24 & really needy & fighting going to bed etc.
Now things are to a point he almost askes to go to bed... I also know that if Aiden is overtired he fights bedtime & yet if he is rested he doesn't KWIM. I also know of 3 other people who have much the same stories to tell.
much the same as Michaela, I think you need to help her learn to relax & she isn't finding it relaxing at bedtime, thus the need to stall.
For what it is worth, I'd try getting her to have sleep anyway you can - in the car etc then try earlier bedtime (on a night you can get dh around) & literally read stories, talk cuddle, rub her back etc in her bed until she falls asleep, with you there... do that for 2-3 days if you can, then work on being there for her helping her relax & going back if she comes out, but NOT ignoring but saying "oh are you finding it hard to get to sleep, do you need Mummy to give you a cuddle, rub your back etc" & then doing that for a moment & telling her you will be back to check in a few minutes & will rub her back/cuddle etc if she still isn't asleep & keep doing that until she does go to sleep... by rights she should take until her "average" time the first day or so, but should get better gradually over a few days.
Anyway having had bad insomnia myself, I have learnt it is being able to relax or not that makes a huge difference in the ability to fall asleep, so I now don't try to get my boys to sleep, but teach them skills to relax & that does get them to sleep
Also some people can't cope with food right on bedtime, as their digestive system keeps them awake... so I would offer the last milk & toast 30mins before bedtime & then only water at bedtime, so her digestion can shut down too.
