doggie proofing

In case you missed my recent blog post on my new place, the photo above shows the sliding doors into my bedroom. I discovered this week that my dog, Lexie, has since figured out how to get into my bedroom – where she's not allowed when I am not home. I came home to the doors cracked open, lots of little footprints around the entrance and a guilty-looking dog.

Any suggestions for a (simple, non-offensive looking) solution to 'lock' a non-locking set of sliding doors? Designers? Architects? Dog people? I also do not own this place, so any solutions cannot involve altering the walls. FYI, both doors slide open.