My daughter is and this is what helped her transition.
There are 21 meals within seven days.
7 x breakfasts
7 x lunches
7 x dinners
She wrote a list of meals that she likes that are omni (meat protein), vegetarian and vegan.
In a day, she would choose one meat meal, one vegetarian and one vegan.
For example:
Breakfast: (vegan) oatmeal with almond milk, dried cranberries, chia seeds, sunflower seeds, shredded apples and walnuts
Lunch: (vegetarian) falafels on pita bread with garlic sauce, onions, spinach, tomatoes, olives, cucumbers and feta cheese
Dinner: (meat/omni): sausage and potato hash with roasted onions, peppers, shredded Brussels sprouts/broccoli and a chimichurri sauce (made of parsley)
The next week, she would eliminate one meat meal a week and make it vegetarian until she eliminated the meat meal or seven weeks
After she stopped eating meat completely, she started changing her vegetarian meals and making those vegan by substituting cheese for vegan cheese, tofu for scrambled eggs or flax eggs for egg substitutions in baking, etc... That didn't take long to do.
All in all, she took around nine weeks to completely change to vegan meals. During that time, she learned more about adapting meals or learning new dishes from various cultures, read up on nutrition and animal welfare.
I always applaud those that can change overnight because it's one heck of an undertaking. It's hard to go against the grain. This may be a bit slower but it worked for her and for the past five years she hasn't looked back. She's inspired me, as I made sure she made the changes correctly as she was 16 then. I'm starting on the 21 meals plan this week.
Anyways, good luck, OP.