pull the plug on what? you spending money or her enjoying the game?
If she loves the game, never pull the plug. Now if the cost of private coaching or travel/tournaments is the issue, definitely pull the plug on spending. If she loves the game she will figure out how to become a great player herself. Hitting the wall, ball machine work, play with local club 'seniors' etc.. Lots of ways to become a great player without playing tournaments or private coaching.