To be fair, Ranma only has shown interest in Ryoga, canonically. What with the whole mirror image kissing him, the Koi Rod of Love deal, tricking him into being his sister/girlfriend/fiancee/schoolgirl in love with him and those ocassions where she wrapped legs around his waist.
Not true, Ranma has been seen blushing when Tatewaki rescued her from the Ghoost swimsuit, she has had several dates with him and she has even kissed him (having taped over his mouth before doing so). Then there are all the times whens he flirts with him, like that time when she was after the doctored photos and made him choose between herself and Akane (she hid in a closet with him) There are plenty of scenes and stories where she is very lubby dubby with him.