Should I stay with her or leave?

There is this girl I like. She's great. We've been talking and she's amazing. But due to... circumstances, I don't see us being permanent. She's really nice and I want what's best for her. I've "left" her and gone back several times. Should I just leave her hoping for her best or should we be together and see how it goes?
Should I stay with her or leave?
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