Saying you have done everything leaves me to believe there is nothing you can do. However from personal experience, I have found that for the one I love, just simply making deep eye contact and letting her know that what I am about to say is 100% true feeling and make my case. Your honesty should come through without a problem if the feeling is indeed true. Your question is rather general and honestly a little confusing with the "believe me that she loves me" (i took it as "make her believe that I love her"). My answer is one of a many possible thousands to your question, all people are different and respond to differently to your actions. If it helps any, write down things you have done on a piece of paper and read it over and over until you find something you can change or something you haven't done. Finally, she may just not be interested in that kind of relationship with you and in that case you need to move on. Life is short.