The person you are having contact with should not be drunk. They will know this before the first session. They are not allowed to be drunk at a contact centre and should not take alcohol there with them.
If they do come drunk the staff on reception will hopefully notice this and deal with this before you see the person you are visiting. If they do not notice this, you might want to help them out by letting them know. If you don’t want to do this, you could always tell the person you live with so that they can work with the centre or the person you’re having contact with to make sure this doesn’t happen again.