The speaker imagines that right next to our world, just a breath away, there is another universe where a different version of her is living the life she wants. That other "me" is happy, safe and warm, has a home and a family, and has never had to look over her shoulder. That last detail is telling. It hints, without explaining, that the speaker's own life involves fear, and that she doesn't have a secure place to belong. The poem doesn't say why, and it doesn't need to.
The ending is the most honest part. She says she both loves and hates the theory. It's comforting to believe that a safe version of her exists somewhere, but painful to know she isn't that version. The word "somehow" suggests she can't quite untangle the feeling herself. The mood is quiet, wistful and a little heartbreaking. The short, plain lines and the repeated "a universe where there is a me" read like a gentle wish, repeated because it matters so much.