Your daughter feeling suicidal has to be dealt with first, you are correct. You just mentioned she struggles with PTSD. That is something she should get help for before she makes ANY kind of commitment to anyone else. She needs to make a commitment to herself, to learn how to process the experience that led to her developing PTSD.

If this guy she is engaged to really loves her and cares about her, he can wait while she gets therapy and regains her sense of "self". These challenges will not go away for her once she gets married either. This is not just a case of the typical nervousness that comes with getting married.

How old is your daughter?