100% width in React Native Flexbox

You should use Dimensions

First, define Dimensions.

import { Dimensions } from "react-native";

var width = Dimensions.get('window').width; //full width
var height = Dimensions.get('window').height; //full height

then, change line1 style like below:

line1: {
    backgroundColor: '#FDD7E4',
    width: width,
},

Simply add alignSelf: "stretch" to your item's stylesheet.

line1: {
    backgroundColor: '#FDD7E4',
    alignSelf: 'stretch',
    textAlign: 'center',
},