Why does my ex-girlfriend still wear the promise ring I gave her even if we are broken up?

Ok so me and my girlfriend were together for about 4 years (we recently broke up)... We are still cool (i still have feelings) but she says she is over me and she doesnt feel the same for me anymore now.. Yet she still wears the promise ring I gave her? It's not like its a 3k ring it was only like $300 and I bought it for her in high school... hmmmm?