No matter what you say, she is not going to listen to you. Since she is talking to you despite of the elders' warning, she loves you very much. Let her be. She thinks that's what makes her happy. However, contact local elders so that they can at least arrange a partner to be with your mom in the morning.
You have to keep yourself cool. Don't lose temper or control. If you do, that's going to be a sign to your mom and the jws that you are demonized. Just let her know that you are concerned with her well being.
I hope things go well with you and your mom.