Tbf, it took me several (rapid) iterations of the idea before my brain settled on a statement of maximum destruction. The reality is that I'd probably laugh and tell her to go fuck herself or just get confused and inform her that I wasn't intending it to be a date and I'm really not attracted to her in that way; I just thought she might be a cool friend to have (if I'm talking to someone then there's a decent chance we're either friends or will be friends in the near future). I imagine both would probably damage her ego as well, but they'd be no where as devastating as my original comment.

In that vein, after I posted my original comment my brain offered me a slightly better one:

[Start with a pause at the beginning because it creates the illusion that her response was unexpected] "...oh, sorry, everyone said I should give you a chance; I just wanted to be nice. I'm really, really sorry. I know you're a very sweet girl and you'll find the right person who can see you for your strengths."