Hi Brad! When linking records across tables, these will always be bidirectional. So in duplicating a record in Table A already linked to a record in Table B, the newly created record will mirror the field data of the original, including the linkage to the record in Table B.
If you find it most efficient to duplicate your records to create anew in Table A (e.g. there are many fields involved that you don't wish to rewrite), I'd recommend manually unlinking the unnecessary record afterwards, and then replacing that linkage with a different record, if applicable. Otherwise, it might save you time to create a new record separately and skip record duplication altogether so that it doesn't cause further confusion.
Let me know if you have any questions about this at all!