No, you can't marry Serana. (Threads will start getting spammed asking for this. Bethesda will eventually give up and allow it/add it/fix it, like they did for Lydia.)
Adding Lydia was not adding a feature, it was fixing a bug. All the official guides said she was supposed to be available (like all the other housecarls). There are others we would love Bethesda to add to the list, but they have not added a single one.