Malia is the Hawaiian form of
Mary. So if one assumes that Malea is simply a respelling of
Malia, that could be its ultimately origin, though it's not how it was originally spelled in Hawaiian.
The source that says "Native American" for "bitter" is confused. The "bitter" is one of the traditional interpretations of the original meaning of
Mary. So that source again is assuming that Malea is a variation of
Mary, this time from some Native American language. However, one must be skeptical about sources which attribute names to a general "Native American" instead of giving the specific language or cultural group.
Where did your parents find the name? That information would be very useful in tracking down its true origin.