Insurance Fraud
You recently interpreted for a Deaf woman filing an insurance claim. She claims she fell at the grocery store and can't use her left leg for 6 months. The following Monday, you go to your first yoga class, and sitting in the class is the same Deaf woman.
An Interpreter's Perspective
I say use your discretion here. You might decide to decline any future assignments for this woman, because you wouldn't be able to remain impartial. You know too much "outside" information.
A Deaf Consumer's Perspective
Avoid making judgements about the woman. Perhaps yoga is a part of her therapeutic treatment. If you know the woman well and feel that your interpreting might be affected by your suspicions, you might ask her about it casually another time.