Panic not. It's a standard therapeutic boundary which my t certainly has verbalised several times when going over boundaries. She often goes over them again, not because I am at all violent, but because she wants me to express some anger and she is trying to show me that apart from hitting her or damaging the room I have free range. Maybe yours could be doing the same? I've had almost identical emails from my t and I think she means them to be reassuring. If you could have this conversation with her it would probably help but if not hopefully enough other people will have had similar comments to put your mind at rest.