Yes, unfortunately Susan falls squarely into a weird sort of place in the fandom - it's almost like any female character from Supernatural, except most of the fangirls aren't protecting a slash relationship (except for the Harry/Marcone people, who didn't seem to be active on the board I was reading.) They want Harry/Murphy or an eventual Harry/Molly and there's a lot of really crappy stuff said about Susan. Thankfully, she does have her defenders, but eesh.