Dean, definitely an excuse. Most women who claim to be open-minded about sex would be more than happy to watch you get off. Plus, you sound like a pretty considerate kind of guy, so I'm guessing that if you thought she would get offended, you wouldn't have done it in the first place. I say you're probably better off without her

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I am certain of nothing but the holiness of the heart's affections and the truth of imagination. What the imagination seizes as beauty must be truth - whether it existed before or not.
-John Keats