Your security deposit is for breakages, lost or unreturned keys etc. It is not for a broken cup or plate. Your cleaning deposit, if applicable, is for cleaning the apartment after you leave.
The owner cannot keep your security deposit for cleaning. If she is witholding the deposit she has to give you a reason. I would definitely complain to the website owners about this one.
My son rented an apartment in Majorca this year and my bank account was used for the fund transfers. As soon as the apartment owner had the money her friendly attitude changed for no reason whatsoever. I contacted her, 10 days after he returned, looking for my £250 security deposit to be returned via bank to bank transfer, same way as it was sent. I got a very curt reply saying that her terms and conditions were that it would be returned after 28 days. It eventually arrived by cheque in an envelope and not by bank to bank transfer as requested.
A review of this apartment will be written shortly outling both the positive and negative of this rental experience. Others can then decide.