Cro is right here. You need to have a bit more purpose and specificity to get the girl engaged to answer. Essentially, you want to make it as low of an effort as possible at first for her to respond. Sort of like lowering the entry bar so to speak. Then, once she's engaged, bantering etc. you move on and you can ask larger, possibly 'deeper' questions.

For now, have some patience (ik it's harder than it sounds cuz it's tempting to just throw in the towel) but if you're genuinely attracted/interested in this girl, you should rengage in a couple of days with something like "not even gonna tell me why you became vegan?" or something along those lines, a mild takeaway. But be sure to wait 2-3 days.

Let me know how it goes and hope this helps bro