Take small steps with your mom and do things that are fun to introduce her to the lifestyle. Offer to make her meals and see if she'll watch the documentary "Forks over Knives" with you. Aim for progress not perfection. My mom is not a vegan either and at one point was very defensive about eating meat, she is now opening up to the idea of being plant based and has even bought a low fat vegan cook book. She's a bit of a finicky eater and is worried that she won't enjoy the food, but she's now starting to be interested in it. So be patient and keep insisting on healthy lifestyle choices. I wish you the best with your mom.
Peace and Health