Tell your daughter to do things she enjoys. Almost everyone I know in a good marriage met their significant others when they weren't looking for one and was enjoying their lives and time. I have this belief that if she is actively pursuing things she enjoys and not actively looking for someone, she'll meet the right one because fate, God, or whatever higher-being will make things work out. The only thing she needs to do is to go out more, be active in a community, and do things she is passionate about.