Just wanted to share....
BTW, promise rings aren't always for couples....in my case, they are to symbolize the pure love between sisters.
Here is my ring (My sister is currently wearing hers and they are both the same style, so I only need to show one):
(Promise rings are bestowed to symbolize a promise that one person makes to another. In some cases, promise rings are precursors to engagement rings. While the latter symbolize a promise to marry, promise rings can stand for many other kinds of vows. -- Ask dot com)
You should have told her verbally and spent the money on beer.