Havers character change after the first series

I've just watched a lot of these on the Drama channel's marathon weekend. Over all I thought they were pretty good stories with generally likeable characters and good guest stars, even if the whole concept is a pale imitation of Morse.

But what struck me most is how feisty and sharp witted Havers is in the first series, especially in the last one when every other line is her standing up for herself and her working class roots, commenting on the manners/behavior of others. She really stands up for herself and her class. But from the second series onwards it's as though she has had a lobotomy, not the same character at all.

She lets everyone, not just her superior officers, get the better of her. She let's them talk about her as though she were invisible, she gets put in her place constantly and she lets Lynley keep calling er 'Havers' all the time even when they're sharing an off duty moment. And she keeps calling him 'sir' all the time, even when they're sharing an off duty moment, which is really infuriating.

What happened? Did a different writer take over from series 2? Whoever is it has completely misunderstood her character.