I am sorry that your T has repeatedly let you down.

Occasionally I've been in a spot where I have really needed to get something back from people who owe me paperwork and/or money. I like to write them a polite reminder, then I send a self addressed stamped envelope for return. It cuts down a step for them to do it, and seems to work pretty well. I don't know if that would work for you, but I think that I'd be reluctant to call her again and I agree with the others to keep the GP out of it.