instead of hurting yourself in front of her, could you tell her you want to because no words seem to describe the depth of your hurt, shame, embarassment, etc? sometimes there are no adequate words to describe the magnitude of something... aside of hurting yourself in session, is there any other way you think you could express yourself? is there some music that really speaks to you about how it feels? or maybe some art or image (either that you do, or that you stumble across online or someplace) that shows what it feels like?
honestly, depending on the severity of the actual injury, and depending on your t, harming yourself in front of her on purpose could end with a lot of unwaned consequences...