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I agree with most of the advice already posted and of course, our various supportive words actually do help.
However, I think it's good that your beloved has the strength of character to be upfront with you even if it hurts. If you really love someone it tends to be in spite of their faults and no-one is perfect anyway. On the other hand, if she doesn't love you enough, then it's time to move on.
Whatever you do, don't dwell on the idea of her and other guys - All that matters is you and her and whether that works, or not. You need to be more selfish (like me!).
Be your own complete person and never split yourself in half for the sake of any other human being. That expression "my other half" is total rubbish and doesn't reflect well on anyone who thinks like that.