Really, this is nothing to joke about. Some kids are very innocent and naive and they can actually be extremely terrified. Sometimes they hear horror stories of the wedding night from their friends which is really a cruel thing to do and so they don’t know better and if they don’t have a good person to talk to and help them have a better understanding they can really freak out. This can be very serious and very damaging to a young person either boy or girl. If that happens to be the issue.
On the other hand if she has a fear of the chassan himself, because of something he said or did, or something she found out about him, she really must talk it out with her parents or someone she trusts to help her figure out if she should move forward of call it off. She needs to know if it is just nerves or if it is her inner voice telling her to be smart and not make a mistake.