Violet Hunter from Copper Beeches is written as lesbian in the slashfic more often than anyone else, I think (I haven't read her story for a long, long time though, so I can't make any promises about the canon.) I think that there's a bit with Holmes and her that is sometimes read as attraction but could get a queer reading.

I think Violet Smith from Solitary Bicyclist is basically the same character as Violet Hunter, so maybe her too?