I think it sounds like she thinks the glove is hers and not yours. So teach her it is your glove and you are letting her play with it so when done. Have her out and then tell her all done or finished and walk away with the flirt pole with glove on it.
This whole "all the toys are mine" concept that so many people get hung up on really has very little to do with this, or anything else, honestly.
But beyond that, the attitude described of "it's mine and you can't have it since you didn't out" will just make the dog less likely to out and more likely to hang on because everytime she lets go she is punished, not rewarded.
If one always equates letting go with the end of the game, then of course the dog isn't going to let go. Why would she? It is in her best interest not to because when she does it means all the fun goes away. Dogs learn much better when we show them that the things we want them to do bring reinforcement in the form of getting things they like. Certainly not in the form of removing things they like.
Right now she is reinforced for keeping the toy. Nothing good happens when she lets go. And having the toy in her possession sure beats having no toy at all, or ending the game.
Easiest way to teach an out is to make it GOOD for the dog to out. Not bad by ending the game. Trade for a higher value item, so the dog learns giving up what she has is an opportunity to get something even better in order to establish the understanding of what "out" means and the dog seeing it's a good thing to do. Then move onto showing her that letting go brings the prey alive again, making the game resume and things even more fun. Lock up the toy so there is no reinforcement and no fun in her holding on, and wait her out. When she lets go, play again. Not the opposite.