Well the main idea is that as Sarah is hanging around with Karyn she is pushing Karyn to try more Sarah-like things.
So basically while Karyn is still fighting and trying to figure out what is going on with Miss Fine Karyn is changing in some ways without realising it.
She won't become exactly like Sarah used to be (that's more Zoe's path) but she will be a bit less of a tomboy.
Hope this helps
