No, I don't believe she should put off her marriage unless she has doubts about her fiance or she elects to do that herself. This should be a happy time in her life. Given that the wedding is imminent have you considered trying to be more positive about your new family member to take that extra stress off her. He is a very significant part of her life. Wouldn't it be less stressful for everyone involved to try and make these relationships work and it would probably mean the world to your daughter. Right now she needs your support. If her marriage is not successful over the long term she will need your support too.