It sounds like your plug is a 5.5mm/2.5mm (OD / ID) whereas the wife's is a 5.5/2.1 - those are pretty common sizes. That's just an educated guess without seeing them, but chances are that's what you have.
You can try a new power brick, but there's a chance something you can't see is broken in the jack on the laptop - it's something you're going to need to check with substitution. If you get the same result with another power brick then your problem is in the laptop itself.
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