“Fun never comes free.” When you met second time you both knew the status of your relationship and still went on for fun, I suppose. Now you are being asked to pay for it. You may stick to your decision and at the same time convey her relatives about her consent for not getting married to her. If she knew that you are not going to marry her before hand and now putting pressure to get married, she is exploiting the situation. You should not succumb to such pressure.