His ex showed up after 6 years?

He was very hurt in past relationship. After 3 years of breakup he met me, everything was fine and then she showed up. She wants to meet him, talk to him, start everything over again. I feel like shit, i know that nothing depends on me right now, i just try to do my best to help him to cope with his feelings. I just feel that shitty feeling that he will come back to her, that she will do or say something that will make him come back to her. I'm afraid of losing him, he says he loves me very much and she means nothing to him, that he has only negative feelings towards her, but i just feel like some person just interrupted between two of us... what should I do? I just feel very very bad.
His ex showed up after 6 years?
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