Originally Posted by VamPyroX

Have you expressed your concerns to your supervisor? Explain that a schedule needs to be kept in order to make things easy. By having your interpreter taken at the last minute forcing you to reschedule is costing your company additional money. If your co-worker's supervisor keeps doing last minute meetings, then it's time for a second interpreter.

From what you've said, it sounds like meetings are normal for your co-worker... to a point where a full-time interpreter could be beneficial for your co-worker and with you having your own interpreter.