[Vuejs]-How to make an object reactivated in vuejs2?

You indicated one-way binding :value="column" which means only to show a value and not to save its changes back to column.
Try to use the v-model directive:

<q-input square outlined :label="key" v-model="tableColumns[index]" />

P.S. and use index as a key only if your array is not modified in terms of its length (i.e. adding/removing items). Otherwise, it’s better to use objects isread of strings with unique identifier field values among other fields.