v-model value inside v-for loop is not unique.

This is my template:

   <template>
      <div
        id="FAQ"
        v-for="(question, index) in questions.slice().reverse()" 
        :key="index"
        class="m-2 col-7"
      >
          <div v-if="getloggedUser.role == 'tutor'">
            <div id="divQuestion">
              <p class="m-5">{{ question.text }}</p>
            </div>
            <div id="divAnswer" class="mt-2">
              <p class="m-2">{{ question.answer }}</p>
            </div>
          </div>
          <div v-else>
            <div id="divQuestion">
              <p class="m-5">{{ question.text }}</p>
            </div>
            <div id="divAnswer" class="mt-2">
              <p class="m-2">{{ question.answer }}</p>
            </div>
            <div v-if="question.answer == null" id="divPsycAnswer">
              <textarea cols="60" rows="3" style="border-radius:12px" v-model="answer.text"></textarea>
              <button id="btnSend" @click="publishAnswer(question.id)">Responder</button>
            </div>
          </div>
      </div> 
   </template>

This is the script (data):

  data() {
    return {
      // arrayFAQ: [],
      form: {
        text: ""
      },
      answer: {
        text: ''
      },
      questions: [],
      message: "",
      loading: false,
      id: null
    }
  },  

This way, everytime I write in one textarea, I write for all the others. I have tried adding [index] in the v-model but there's this error: "TypeError: Cannot use 'in' operator to search for '0' in "