I have a 3 titles on Text's components and a divider below each one as View's components. They have the following styles.
title: {
...PosText,
color: Palette.TEXT_ON_LIGHT,
paddingBottom: 9,
},
divider: {
height: 0.5,
backgroundColor: Palette.BACKGROUND_DIVIDERS,
marginBottom: 1,
},
I should see the title and a line divider beneath them but the first divider gets lost.

You can create a quick SeparatingLine component and set the borderWidth as you wish (add margins as needed).
I am using something like this in my project:
export default class SeparatingLine extends Component {
render() {
return (
<View style={styles.separatingLine} />
)
}
}
const styles = StyleSheet.create({
separatingLine: {
borderWidth: 0.5,
borderColor: 'grey',
},
});