I know how you feel. I held onto my Mary statue for years after she'd lost an arm (not salvageable via gluing). I couldn't bear to be the one to throw her away. I don't remember ever throwing her away, but I have no idea where she went!

Back in CCD (think Sunday School for us Catholic kids) my 5th grade teacher was an old, Italian Nun from Sacred Heart. I kid you not. In the middle of a session Christ fell off her Rosary. She just reached into her top desk drawer and used the Super Glue to re-attach him. In a moment she said "Good as new!"

I say if your mother's crucifix means a lot to you then do as the nuns do If it doesn't mean much to you then you are safe to chuck it as it is a symbol. I have also tossed assoted broken stuff and I have yet to be struck by lightening (looking up at clouds to double check)