You'll have to emit an event so the parent component can react to it: https://v3.vuejs.org/guide/composition-api-setup.html#accessing-component-properties

Untested:

<template>
      <div class="column" style="width: 300px;">
        <q-btn @click="sendEventImage ()" style="margin-top: 16px; margin-bottom: 32px;" outline color="white" text-color="black" label="Procurar imagem" />
        <input style="display:none" ref="EventfileInput" @change="onEventFilePicked" type="file" name="upload" accept="image/*" />
        <q-img class="w-30 h-30" :src="imageUrl" />
      </div>
</template>

<script>

import { defineComponent, ref } from 'vue'

export default defineComponent({
    name: 'FileUpload',
    emits: ['imageloaded'],
    setup (props, { emit }) {
        const imageUrl = ref('');
        const EventfileInput = ref(null);
          
        const onEventFilePicked = (event) => {
            const files = event.target.files
            const image = files[0]
            console.log(image)
            const filename = files[0].name
            if (filename.lastIndexOf('.') <= 0) {
              return alert('Por favor adicione um arquivo válido')
            }
            const fileReader = new FileReader()
            fileReader.addEventListener('load', (event) => {
              imageUrl.value = fileReader.result
              console.log('setimageUrl', imageUrl.value)
              emit('imageloaded',imageUrl.value);
            })
            fileReader.readAsDataURL(files[0])
        };
        const sendEventImage = () => {
            console.log('sendEvent preview')
            EventfileInput.click()
        };
        return {
            imageUrl,
            sendEventImage,
            onEventFilePicked
        }
    }
})
</script>

A few remarks on your code which I changed in my example:

• don't use this in setup()
• I recommend using const for refs to prevent accidentally overriding them and losing reactivity.
• you can define template refs like normal refs: https://v3.vuejs.org/guide/composition-api-template-refs.html#template-refs