There's no actual video, but Over My Head by Fleetwood Mac is great song to listen to and use your own experience as the video maker. An oldie but goodie..
After reading your details that follow your question, the song that I provided most likely wouldn't fit. I'm wondering are you trying to tell her you're the wrong person for her, or is she in a relationship with another that you feel isn't the right person for her? There's all kinds of songs about love out there. Thank you!