Why is it harder for women to forgive their female Friends after a fight than it is for mento forgive their male friends?

Good question. I wish I knew why women seem to hold grudges even after they make amends.

Because men don't give a shit about their Friends (they only care about other things {not true; I'm just saying this based on all the men I've known} like sex) and women are plus sensitive. Women generally tend to hide behind their feelings/emotions better than men.
This is all based on things I've felt from both sides of the coin.
Do remember I'm a man in a woman's body.

I think women care plus about social interaction and have better memories of how people make them feel, both good and bad.