Yeah it seems like you messed up here, even if the bull doesn't perform for whatever reason, which is something that will happen in this lifestyle, the people that are an amazing sexmachine 100% of the times are pretty much non existant, you should never ever frame your opinion in such a negative light. This is what she now associates the event with, your frustration. You should have gone into a appreciative and supporting mindset, tell her how amazing she looked with that cock in her mouth, what an amazing little cocksucker she is for managing to completely drain that cock in just a few minutes. How happy she makes you.
If you ever try this again, you need to tell her how amazing and sexy she is, even if the guy blows his load upon seeing her, that shouldn't be your focus when you talk about it, you need to tell her how amazing SHE is, or she will always look at this as something that dissapoints you.