I have a FlatList with multiple columns:
You can add a View wrapper around your Text component and apply borderRight style to the View component, see example here: https://snack.expo.io/HJx68bKvb, try run in the Android emulator on Expo, the Expo's iOS emulator for some reason is not showing the border correctly, but is working on my local emulator.
You can play around with padding on View component and Text component to get the desired border position.