TTE might come, might not come,he might consider, he might not. So that is a risk.Why dont you think of changing the boarding point ?Then you dont have the fear of losing the seat.
I understand that you wish to travel with your friend from Betul to Narkher, while your friend will continue till YPR. This is also possible, just buy a Genral ticket and sit with your friend.Give the excess fare to TTE if he comes.