With Sera, just remember, people can and will change. The Sera we see is obviously troubled in some ways; that's why if you're tolerant to her she will slowly respond to you. If you are not she will flip out. Sometimes she will flip out anyway, because inside she's quite obviously caged and a little afraid, likely from how she grew up, and since she isn't particularly skilled at words outside her comfort zone you can't really take everything she says at face value.
I see her as I see her dialect, as somebody who doesn't natively speak like that. You've got to think about what is really being said, not only catch on to the funny or shock-value words. Makes her interesting to me - although I admit she does have very nice hair, too.
As for sex scenes, I always am a little cringey with the actual action. It's not easy to make that look natural; I like the scenes because of the opportunity for dialogue that arises though, and some things -are- sweet. 