Romance (love): Should I accept a girl who dumped me, and after 1 year of breakup wants to get back together?
There are a few things that irritate me about the details of your question. However, I said that as lovingly as I can. ♥
Love is not a liquid that is measured with a spoon or a cup. It has no amount. It is or it isn't. It's a state of mind. A way of life when you're in a relationship. You can't love someone ‘a little' or ‘to a certain extent'. If you do, that's not love. That's an alchemy of lust, guilt, frustration, anger, nostalgia and hope mixed together. The exact ingredients are specific to the individual of course.
When you said it was magical, it was magical to you. From my perspective, I feel like it wasn't really her that you fell in love with, but the idea of her. You placed her on a pedestal and worshipped that idea of her. You fell in love with the mask she put on herself. Then when she left you, she shattered that mask, that illusion and you were blinded to the reasons why she left you. You said she left you for no reason. Obviously there is a reason. She left you because she wasn't in love with you. She was in love with her ex boyfriend. You were just an anchor, a back-up in case things didn't go her way with the ex.
However, unlike most of the other answers so far, I am going to suggest an entirely different thing to you. Personally, I believe that third party advice hardly ever works for people seeking for advice on relationship matters, especially if they already have an idea what they want to do. I feel the majority of the time, people asking for relationship help are actually seeking confirmation for what they already chose to do.
So my advice to you is this: take her back and see where it takes you. If things work out, which is a possibility, then great, you would grow old together, look back and realize this was a decision well worth it. If things don't work out, you do some self reflecting, build up your self esteem, get a broader view of the world and figure out what sort of relationship you really want in the future.
This whole ‘Should I trust her again?' question is pointless because no one can answer that question for you. Go in front of a mirror and ask yourself, "Do I trust her?"
Trust is a whimsical thing. While trust is important while within a relationship of sorts, it's not nearly as fundamentally useful outside of one. Rather than ask if you should trust her, you could just ask if you want to take the chance. That's the more important thing: give yourself the opportunity for further experiences or move onto new ones.
Clarity on my point about trust being a whimsical thing:
Trust is whimsical because it solely depends on the individual's self esteem. While it is true people gain trust in varying aspects with other people coinciding experiences they had with those people, ultimately, that trust is marred by one's own issues. Those issues can be quite expansive.
The way people gain and earn trust is based on the amount of filters that are set between them. The difficulty to pass through those filters depend on the dynamics of that relationship, as well as the perception of each individual.
Mechanically, trust isn't a bridge between two people, but rather, trust is a bridge between your desires and your intuition.