I was kinda in the same situation as you back in June. I know this may sound a bit cliche but seriously, keep yourself busy with other stuff. In August,while I was still thinking about my guy, I went off to Wales to climb Mount Snowdon and then I was sports coaching kids afterwards. I realised after that I hadn't even thought about him. Now,if anyone mentions him,I don't really care that much.So to you, my best bit of advice would be to keep yourself busy which will allow you to hopefully get over her and next time someone mentions this girl, you won't be too bothered.
Good luck!x