The question “does size matter” needs to be differentiated from “does size make a difference”. Of course different sizes will feel differently. But in the larger scheme of love, intimacy and sex, even casual sex, penis size is not what matters most. Therefore it matters at least "less". Smaller penises feel differently; how could they not. But different is not automatically worse. Maybe smaller will be novel, or surprisingly pleasant, or more versatile, or even preferable… it really is about she sees it, or feels it… Many women have experienced a range of sizes and know what to expect with a smaller man. A woman may be initially relieved or disappointed. Being smaller she may understand that you may be nervous and insecure. I bet she has some insecurities too. I suspect the majority of women will be tactful and respectful and if you do all you can to fully invest yourself in the moment and exceed her overall expectations there will be little if any ongoing issue. In any case, take the initiative. Surprise her with enthusiasm, creativity and spontaneity. Create and exploit positive energy. Do everything you can to make the moment and the mood relaxed and enjoyable. In my experience "Sighs Matter".