No, she was always a big-headed bitch, she was just hiding that side of her. I will never believe that a person who has been sweet all of her life would change because of __(insert reason)___. Just like suddenly coming into money doesn't change you, it just brings out who you always were, exponentially. The original cast members were earning $300 or less per week before the show started, but now all have at least six figures in their bank accounts. That made them become more of who they always were, which is total effing douches and assholes.
I don't think Brittany's a bad or malicious person, but this sweet Southern-oh-shucks-y'all persona is just an act. Sweet Southern girls don't lie about never having watched reality television, pick the shittiest guy from a show, move to LA and get her boobs done. She's always wanted to be famous, she's always wanted to move to LA and was just waiting for the right time.
My mother is the same. Everybody sees her as this super-nice Christian, church-going, sweet person who cares about everyone. But of course I know better. When I was young, she would abandon and neglect me for days at a time, disappear somewhere when she felt like it and left me alone to deal with my very abusive father and didn't protect me from him. So now, I can spot fake-nice people very quickly. Having said that, it's really difficult to convince others what I can see in those types of people, because they tend to only see the façade. Or maybe that's just what they want to see.
That's for next season of Vanderpump Rules! You can only have one couple be the centre of attention per season. Nobody would want to share the wedding limelight with another couple, especially if Jax is part of that.