Segments overflowing in parent view with only three buttons.
It looks like as:

Can not apply the styles also.
@dev-pacific22 try changing segment button's padding (paddingLeft and paddingRight).
Sample code
import React, { Component } from 'react';
import { StyleSheet } from "react-native";
import { Container, Header, Left, Body, Right, Button, Icon, Title, Segment, Content, Text } from 'native-base';
export default class App extends Component {
state = { selected: 1 }
render() {
return (
<Container>
<Header>
<Left>
<Button transparent>
<Icon name="arrow-back" />
</Button>
</Left>
<Body>
<Title>Forms</Title>
</Body>
<Right>
<Button transparent>
<Icon name="search" />
</Button>
</Right>
</Header>
<Segment>
<Button first active={this.state.selected === 1} style={styles.segmentButton} onPress={() => this.setState({ selected: 1 })}>
<Text >Get Started</Text>
</Button>
<Button active={this.state.selected === 2} style={styles.segmentButton} onPress={() => this.setState({ selected: 2 })}>
<Text>In Progress</Text>
</Button>
<Button last active={this.state.selected === 3} style={styles.segmentButton} onPress={() => this.setState({ selected: 3 })}>
<Text>Completed</Text>
</Button>
</Segment>
<Content padder>
<Text>Segment</Text>
</Content>
</Container>
);
}
}
const styles = StyleSheet.create({
segmentButton: {
paddingLeft: 0,
paddingRight: 0
}
})

Released with 2.5.0
Most helpful comment
@dev-pacific22 try changing segment button's padding (paddingLeft and paddingRight).
Sample code