I think you're gonna feel worse if you don't tell her. It sounds like it would be best to sit her down and explain what happened, and apologise for it. She'd appreciate you telling her, rather than the chance of her finding out later. It was a bad move, but you can still take responsibility for it and try to move on with her. It would be worse to not tell her, another bad move, and just let things like this rack up, you know?