Heaven you're doing a great job - you've been given some great advice there, just wanted to add my vote of encouragement

I think you hit the nail on the head when you yourself said:
Eventually goes to sleep but sometimes it has taken up to an hour!! The crying she does is loud but I don't feel like it's a distressed, sad, upset cry. It's like she's angry with us. She wants to be fed or rocked but we're not giving it to her. Eventually she realizes she will have to go to sleep on her own and she does.
Listen to yourself hun

It might take up to an hour now... but in a week it might take half an hour... and a week later it might take ten mins... and then soon she might not even stir at all