But, she can't be researching everything all at once, only the things that are most important to her. Even if she finds information that contradicts JW teachings, that doesn't mean she will right away accept the new information. After being a JW for sometime and in being required to fight against opposition, contradictory info is often confusing and is usually first rejected. The process of becoming an ex-JW often can take years, sometimes decades.
Although it may be frustrating for you now, please remember, your mom by leaving the religion, has opened the door a little to you being potentially able to celebrate Christmas. If she hadn't allowed herself to consider leaving that religion, you would have no hope of celebrating, at least until you are old enough to move out and start making your own decisions, with the potential of being shunned by your own mother.