Hmm, I don't remember Eola being marriable in the vanilla game. Still, it'd be a match -- my dude has been eating tons of human hearts lately. In fact, sometimes I go through to level archery, then transform and go through backwards for a free buffet.
As for Serana, she's not bad. I often start Dawnguard at LV1 for the crossbows nowadays, so it's easy to get sick of her by the end, though. Kind of a shame they didn't make her marriable from the get-go, since you can (IIRC) make your spouse a vampire like you.
DuneMan posted...
Someone mentioned Ysolda as another option, and she works well if you choose to live in Whiterun itself. The Sleeping Tree Sap thing puts some people off, but it's really the vampires that take it to next level by mixing it with Skooma and the Redwater Spring. The Sap on its own just sort of makes you useless for a bit.
I sorta remember her quest...something about fighting a giant in a cave on the plains. I can solo giants nowadays (and often have to, since they can spawn outside my swamp mansion) so it's not a big deal, though.