Maybe a few months ago she actually still needed two naps and that was the reason why she woke after 45min. It's usually a sign for overtiredness, that's why I suggested cutting the A-times and lengthening the night.
I would stay with her to fall asleep, just put a chair next to her bed and sit there until she is asleep. When she sleeps longer and isn't OT, she can learn to fall asleep without you, but one thing after the other
Winddown at that age would include the explanation that it's bedtime soon. Then the bedtime routine, eg: dinner, bath, book, bed. maybe even a bottle still, I don't know. It has to be darkish, quiet and calming.