VGFacts

Early artwork of Harvest Moon:A Wonderful Life shows the character Nami (the red headed girl) with unkempt, messy hair.


However, by the game's release, her hair was now straightened out.



Now, what is pretty cool is that she makes an appearance in later Harvest Moon games. In these later games, her hair is messy again.
Harvest Moon DS:


Harvest Moon: Magical Melody

Figure it'd be to crack down on how much space she took up? More detail, more space needed to put said details.

Indeed. It was probably just to reduce the number of polygons on her model, not only for space, but for performance. Harvest Moon games tend to be a little sluggish, so it's likely that they had to simplify some things to make it run on the hardware. Consoles typically have very limited RAM, relative to computers available in the same time period.