Have you considered what is trivial and lighthearted to you might be deeply offensive to her? You might say "that is exactly what I am trying to change" but to that I would say "why". Unless a person is explicitly causing harm either by doing anti social things or inciting people with speeches to do anti social things, or forces their belief system on you, what someone believes in or finds funny is no one's business. I guess your mother isn't any of that - she's just a law abiding woman with a certain religious faith that makes her life feel meaningful - so leave her alone.
It also seems that you are to quick to relate religious people with religious extremists, which is flawed. The whole idea of atheists having to "wake up" religious people is quite cocky and indecent. Also the assumption that religious people have "impaired judgement" is deeply offensive. If anything, its the atheists who are extremists with impaired judgement because they think they are better then the religious people.
I used to be one of these cocky atheists in my early 20s and used to constantly bother my deeply religious mother until one day she told me off. She basically said why do I bother her when she doesn't force me to follow the religion (she did like any parent till I was a teen and rebelled and then left me alone). That was a wake up call to me. Of course, my cockiness will come right out whenever a religious relative or colleague tries to mock my lack of faith or give me unsolicited advice with religion based arguments. But in general, I don't try to be holier than thou and look down upon religious people or interfere with their faith.