If Gabrielle's message contained information that is only intended for the recipient, the message should be marked to discourage it from being shared? private
normal
sensitive
delayed​

Private.

From the lack of information in the question, it can be assumed that the message arrived in a timely fashion.

As it is not said that the message is urgent, it is not sensitive to a reply.

Finally, there is a caveat to the message in that it is only intended for he recipient, therefore it is not a normal message.

This leaves one answer and one only: Private.

Cuz maybe it is inappropriate