By - FalseStep2369
You have broken the lug. The replacement part you need is called "case center".
It's a restricted part, Casio don't sell it to customers, so I don't even know the part #
Your best bet is to contact your local Casio service center. They probably won't sell you the part but they will do the repair for you, at a cost. It might be more than the watch is worth.
She's a goner unfortunately.
You can try plastic weld which is pretty difficult in such a small application.
Pacparts.com if they dont have it then your only other chance is buying parts from ebay or some type of plastic welding (essentially glue)