But she can refuse to give me a reference should i letnew employer know that this maybe the case? or wait and see?

So a really long story but here is the shortened version, yesterday was my last day at my former employer, when I resigned from my position I had told them I was resigning on the basis of lack of support and ill health (the job was making me very stressed, depressed and I had anxiety attacks). I did not go into details about my health problems I was vague about my reasons. On my resignation I informed them I did not have another job to go to. About two weeks later I got called by a recruitment agency to say there was a great opportunity at a good firm and they would like to interview. I was still working my notice period, and took the time off as annual leave to attend the first and second interview. I was offered the job and accepted. I at this point did not think it necessary to tell my employer because I had already handed in my notice and was simply working my notice period. The company that offered me the job then wrote to employer asking for references. I got called into the meeting room and she basically called me a liar and told be I had been dishonest about my reasons for leaving, she even brought up the fact I was a christian and I had lied. I explained to her at the time of resigning my reasons were the truth and the job offer was unexpected and after I resigned. I have to repay my study fees and I last week asked if I could repay these over a 4 month period which she agreed to, in the meeting yesterday she told me that agreement was null and void and she expected all her money on her desk on monday and said that even at the point of agreeing the repayment of my fees I did not tell them. She kept calling me a liar and told me that she could report me to the regulatory body for the financial services for dishonesty and I could be struck off and not be able to practice. She then asked me to leave her office which I did went upstairs to another meeting room and spoke to a colleague as I was upset about the whole situation, she came in and told me to leave the premises. I picked up my stuff and left. What I would like to know, was I in the wrong for not telling them about the job? Bearing in mind, I received the invitation to interview after I resigned and therefore accepting the job offer after. does it make me a liar, therefore questioning my character? I am not sure if she will refuse to give a reference or not, should I let my new employer know that she may or may not give me a reference? Does she have any grounds for getting me struck off? and therefore ruining my career? Where do I stand? Any advice would be greatly appreciated.