My fiancee wants to call off the wedding?

My fiancee Dawn told me she intends to not go through with the wedding. She told me she is sick of how interfering my EX wife Stacy in our business. She told me i need to grow a set and stand up to her for the ***** she is. She told me she feels like i care more about what Stacy thinks than i care about what she thinks. Stacy and i don't get along but she is the mother of my daughter so she will always been a big part of my life. I'm tired of fighting with her and have decided to just let it go. Dawn and i were scheduled to get married in July but she told me said she won't marry me unless i cut Stacy out of my life. What should i do?