I've always read it the same was as theplottwist's said, Lisa is wife number two, but the reincarnation of Elisabeta. Seeing as Stoker's Dracula is considered 'canon', and in the Sorrow game, Mina Hakuba sounds similar to Mina Harker, I read it that Mina Hakuba is the reincarnation of Mina Harker, who was in turn Lisa's reincarnation - they're the same soul, Drac's soulmate.
The two wives thing also fits in well with the history of the real Vlad Tepes, who reputedly had two wives, the first of whom, according to legend, flung herself from the 'castle' - the fortress Poenari - into the Arges river, which is where that bit in Coppola's Dracula comes from. His second wife was Ilona Szilagyi, cousin of Matthias Corvinus, king of Hungary.