What do u do about a lesbian girl who likes u??!!! HELP ME!?

there is this girl named amanda in my grade. Everyone knows that she is a lesbian, but she has yet to ask any girls out. Last year she asked one girl out, but that girl was transfering schools at the time. Well, today she went up to me and was like, "hey, dawn!!! i like u....go out with me??" i was like, "no!" i kinda feel bad though cause he is kinda werid, but i could have been nicer. I was just so embarresst cause everyone was like, "hahahah! amanda asked u out!!??" i am totally embarred, and scared. Should i tell amanda sorry, or just let it hang. People might think im werid if i say sorry thou! what should i do?