Why don't you just make a ring out of a silver coin, if she really loved you then that will be enough, if not then maybe you need to rethink the engagement thingy. 
With a silver coin, some tools, and a little bit of time, you can skip the jewelry store and make a simple ring at home.
http://www.wikihow.com/Make-a-Ring-...-Silver-Coin
With a silver coin, some tools, and a little bit of time, you can skip the jewelry store and make a simple ring at home.
http://www.wikihow.com/Make-a-Ring-...-Silver-Coin























