I think Gallstones are formed due to a series of factors, one being high animal protein diets which are also high in fat. But there are other factors like stress, not sleeping early on a schedule, not drinking enough water / fruits, eating without finishing your digestion, overeating, going to bed with food in your stomach. You can have an acidifying body without eating meat, so you have to keep that in mind too.
Ps .- also there are vegetarians that eat fried chips with beer and other processed foods. That is not healthy.
Also the best way for you is to be your own judge, go on a vegan lifestyle for idk a month, then eat meat, see how you feel for yourself.
In my case I experienced acid reflux and bad breath when I did that.