Вы должны поместить весь макет в другой макет и использовать направляющую с процентом 0,7 и ограничить внутреннюю компоновку (то есть синюю компоновку) этой директивой, как это
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
app:layout_constraintGuide_percent="0.7"/>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
app:layout_constraintHorizontal_weight="1.0"
android:background="#43B2FD"
android:padding="6dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="@+id/guideline"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintWidth_max="wrap">
<androidx.constraintlayout.widget.ConstraintLayout
android:id="@+id/csReply"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:background="#20606060"
app:layout_constraintBottom_toTopOf="@+id/tvMsg"
app:layout_constraintEnd_toStartOf="@+id/barrier"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintWidth_percent="0.7">
<TextView
android:id="@+id/tvVerticalLine"
android:layout_width="5dp"
android:layout_height="0dp"
android:background="#4476FC"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/tvText"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="4dp"
android:paddingStart="2dp"
android:paddingEnd="2dp"
android:text="sssssssssssss\nsssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss"
app:layout_constrainedWidth="false"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/ivReplyThumbnail"
app:layout_constraintStart_toEndOf="@+id/tvVerticalLine"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.5" />
<ImageView
android:id="@+id/ivReplyThumbnail"
android:layout_width="36dp"
android:layout_height="36dp"
android:adjustViewBounds="true"
android:background="#F44336"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
<TextView
android:id="@+id/tvMsg"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:text="Heressssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss "
android:textColor="#fff"
app:layout_constrainedWidth="false"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/csReply"
app:layout_constraintWidth_percent="0.7"
tools:layout_editor_absoluteX="5dp"
tools:layout_editor_absoluteY="75dp" />
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="07:43 PM"
android:textColor="#fff"
app:layout_constraintEnd_toStartOf="@id/barrier"
app:layout_constraintTop_toBottomOf="@+id/tvMsg"
tools:layout_editor_absoluteX="133dp"
tools:layout_editor_absoluteY="161dp" />
<androidx.constraintlayout.widget.Barrier
android:id="@+id/barrier"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:barrierDirection="end"
app:constraint_referenced_ids="tvMsg,csReply,textView" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
обратите внимание, что я простодобавили первый макет ограничения и указатель к вашему коду, а также я изменил ширину вашего макета ограничения с синим фоном