Well first of all, please don't replace the word 'beautiful' with anything! Maybe change it to "beautiful, sexy and vibrant", but that's it. Second, the notion that we'd need to attract unavailable women sounds to be originating from a scarcity mindset; if the sub actually works to provide abundant single/available women then you'd be fine without those unavailable women. I personally wouldn't want all that drama and quilt of constantly breaking relationships. Thirdly, I'm guessing when the (male) user's subconscious hears the word 'single', it'll probably fetch what that word means to the user and then start attracting exactly that. It wouldn't just start sending out the literal English word 'single' for women to interpret. But I agree that, to my mind at least, 'available' would seem more appropriate than 'single', because the former feels a bit looser.
Thoughts, opinions and beliefs subject to change without prior notice.