I don't think you should have thrown them away either, just kept them packed away. I understand how your gf must feel, but the others are right - the past can't be erased. Late last year, just before I moved in with my bf, I found a letter by his bed that his ex-gf (from when we were taking a break mid-last year) had written him a month or so earlier that he'd left there (my bf tidies his room about once a year), and that really upset me since I was only just finding my feet in this new phase of our relationship, but he put it out of sight somewhere and I don't think it bothers me now, I'm sure he's prob got a few pics and other mementoes hidden away somewhere, as do I from my past relationships.

The only reason for throwing them out would be if you were looking through them regularly and still maintained feelings for your ex, like mellors said, but even then just packing them away could work.