Setting boundaries (actually honoring boundaries you didn't even set) isn't being rude nor do you have to act rude to set or honor them.
Tell your W enough times when she says ANYTHING that is not child related that you wont have that conversation and eventually she might start to ASK if you if you are willing to talk about other things. She only talks to you about non child related things when she needs or wants something and you allow it.
There really is nothing more to say about the matter. You either do it or don't. If you want something different to possibly happen then do it. If you like how things are then don't.
