It was really hard for me to accept, but when people act that way generally the truth is they just don't feel for you like that, they just need someone, anyone who will make them feel better.
You obviously still care about her as she had become a big part of your life and generally no one spends 3 years with someone they don't like as a person, but you also seem to naturally now be feeling bitter and frustrated towards her and yourself.
I'm sorry to say it 'cause it always really hurts to acknowledge, but I don't see there is much likelihood of you in the foreseeable future ending up together purely because you are unequal in the way you feel about each other and this inequality only heightens her disregard for you in that way.
You mention her friends so I'm guessing she then has people to support her and be there for her while she is grieving. So you should be honest with yourself about how you feel and the reality of her feelings and have no compunction in avoiding her and trying to interest yourself in new things. New things as in friends and activities, NOT a new relationship because you'll find yourself probably disappointed, with someone you are not inspired by or worse unnecessarily hurting someone else because you find your still not over your ex.
Very rarely can ex's still be friends and only if they both don't like each like that anymore. You still do to a certain extent and if you try and keep the door open you will probably get used by her for a bit or you will spend all the time you can with her as "friends" overanalysing everything she says and does, getting jealous and generally getting your hopes up only to have them dashed. When you like/love someone you don't see how they cannot reciprocate or wouldn't if they saw you more clearly, spent more time with you, weren't blinded or knew you better.
Phew…. I have waffled on for ages but I hope it helps and is not too garbled. The main thing I have found for myself to get 'over' someone is always to be honest with myself, how I feel and my motivations.
Try to move on, we all deserve somone who is wise to our [censored], yet adores us anyway