Faith vs Buffy

[Cookie Dough]

Faith was jealous of Buffy because when she first came to Sunnydale she realized Buffy was already set up as the Slayer of Sunnydale and Faith felt left out. She said "It's always about you, Buffy. Everyone said I should be more like you, but has anyone ever said you should be more like me?! No."
So she felt underappreciated because she was a slayer too.

Then in season 7 Amy put the curse on Willow because she felt like Willow could get away with trying to destroy the world, while Amy tried to do some manipulating magic in s6 and Willow got angry at her for it. Amy said "You tried to destroy the world and everyone just forgave you for it!"

When I first saw that I noticed that the minor arcs in each of those relationships, Buffy/Faith, and Willow/Amy were alike because each felt jealous and unappreciated because they were the same as their adversary but treated oppositely.

 

[SlayerThe]

True there are some similarities in these stated rivalries.

But it is easy to assume that the reason why Buffy and Willow are forgiven so easily is because they have both done such good and have a long history of doing so.

Plus the inner circle of the Scoobies is rather tight on forgiveness.