That's odd. It doesn't work for me either now. Try deleting the "learning" part of the link and just click on the learning section.
Of course she is important to you, and that's great. But making everything revolve around her isn't good for her long term mental health. When she becomes an adult, she'll need to learn to negotiate and compromise with others. Not feel less than others (as you perhaps do?) but not feel superior to others, either. Just equal. We don't magically learn these things in adulthood, it has to be an ongoing learning process - three is a great time to start learning.
Short term, children who are in control of the family feel very frightened. They begin to display extreme behaviour because they don't actually know how to cope with having so much power and no boundaries. It is your job as the parent to put those boundaries in place, yes, even if it upsets them sometimes. That's okay because you're right there to help them deal with those feelings. You can help them deal with their feelings while still keeping the message and the boundary strong. This actually helps them to learn how to deal with negative emotions too, which is a really important life skill.
Long term, if she goes out into the world believing that she is special and superior to others, she is going to get a big shock when she isn't treated that way any more. Yes she will always be more special to you than to other people - and so she should be. But it doesn't do any favours to keep her at the centre of your world, because nobody else will treat her that way, and she won't get very far by behaving like a diva in adult life. Worst case scenario, she could even develop narcissistic tendencies and go on to abuse people.
There is a pretty big shift at about two or three. During the baby years, all of their needs are wants and all of their wants are needs, and it's okay to treat them as such. In fact doing so has probably led to the wonderfully close relationship you have now, so it's a good thing. It's just that this dynamic now has to change as she is getting older. It's a good time to introduce the idea that there is give and take in life, and sometimes, she must wait for or give to you, rather than always getting her every whim met immediately. That's a hard transition for her (which is why people talk about the "terrible twos" and the challenges of the toddler period) but it sounds like it will also be a hard transition for you - perhaps, even harder.
I've got some links for you as I think of them but keep talking, too. And maybe see if you can find any parenting classes local to you if you speak the language. Even if you don't agree fully with what the teacher is saying, it's really useful to gain knowledge and support from others.
This is a really long thread, and some of it is hard reading/critical but you might want to have a read - from someone a few years down the line of this approach:
www.mumsnet.com/Talk/behaviour_development/2321246-My-5y-old-DS-bullies-me
Two books I really like are "How To Talk So Kids Will Listen and Listen So Kids Will Talk." and "When Your Kids Push Your Buttons" (the latter has a "profile" of a parent who can never bear to upset their child which you might relate to).
What's wrong with permissive parenting?
Does Peaceful Parenting mean kids do whatever they want?
Increase trust with your child (Pay special attention to the part about boundaries)
What happens when kids rule the roost?
Hope some of those are helpful, anyway.