I don't think it is really a problem - it is a spelling issue - and it can be so confusing - probably one or the other is a Dit name - either Labrie or Mignot/Migneault is most likely, and I have been in your shoes, it will be ok, look up all three spellings and track down the source that is most close in time to the person's birth and that will give you the best information - don't go by other's trees they may be wrong, use them for hints and do your own research. Primary sources are documents that were made at the time of the event - not later compilations that may be in error.
God luck on your quest.