I have the opposite problem! Jersey won't spit the ball out for a tug or another ball! LOL

It sounds like need to teach Paris to "HOLD IT". Teach her to hold the ball in her mouth with the clicker. Start off with just a couple seconds, and work your way up slowly to 15 seconds. Then when she is good with that, you can add it to her runback. When she goes off the box (or picks up the ball off the ground if you're doing dead ball) and starts running back say "PARIS, HOLD IT!"

Good luck!