Leaving tenant dispute over damage

Tenancy Deposits

Hi my tenant left my flat on 31st March. Having checked the property I noticed that the mattress was badly stained, the fridge glass shelf was broken and that there were cutting scratches on the kitchen work surface. On the 9th April I sent an informal email pointing these things out and could we discuss. I received a formal heavy handed letter dated 16th April saying that she did not damage the mattress; that the fridge shelf was broken upon taking up the occupancy and that she used her own chopping boards. Is it worth the trouble taking this on as there is no proof either way and I don't see how the DPS can arbitrate on this one? Regards, Mark