I pity Lydia. No matter how I look at it, I don't think she enjoys a life of breaking in people's house, stealing their belongings (and sometimes souls) and being attacked by dragons every other day. I don't think that's what she expected when she signed to be a housecarl.

Maybe she dreamed of serving some noble Nord lord... or just a nice Nord... or a Nord which doesn't eat bugs and human hearts and perform questionable magic.

When she runs in the front of my fireballs and activate every trap,  think, deep inside, she is trying to give a hint about her level of satisfaction.