Thank you for the information. It helps.
Living with your mother in the home may cause issues in your marriage if the boundaries are not clear. When you marry, you are to leave your parents behind (in a physical and emotional way, not a loving way) and put your spouse first. When you have your parent in the home with you however, this is where the boundaries can get crossed. Your mother is used to having you to herself. She raised you and cared for you and now depends on you for her home. So she has a set boundary with you.
When you marry, however, your husband will replace her as the most important person in your life. If your mother is not prepared for moving aside or does not want to, she can become upset and create issues in your marriage. She may feel competitive with your husband for your attention and either consciously or unconsciously sabotage your relationship.
But if your mother is prepared for the change, it may go more smoothly. She needs to be willing to give you both your space and be ready to live more independently, creating her own social supports and keeping herself busy while not expecting the two of you to entertain her.
Overall, it is better psychologically for your marriage if your mother does move out. Even if she is cooperative, just her presence alone can create a boundary between you and your husband that does not allow for spontaneous closeness, comfort with sexual expression or just the privacy couples need to work out their issues and become closer with each other. But if you feel you cannot ask her to leave yet, work with her to make plans for her to move out. Or create a separate living area for her. That way, you and your soon to be husband can develop the marriage without worrying about your mother being there.
I hope this has helped you,