Factual error: At the beginning of the movie, it was stated that Constantinople was captured by the Turks in 1462. The Turks actually captured it in 1453. (00:00:35)
Factual error: When the Demeter comes to London, there is a wide shot of the ship docking, with Hillingham sitting on top of a hill overlooking the city of London - you can see Big Ben, the House of Parliament and Westminster Abbey. However, when Mina opens Jonathan's letter earlier in the film, there is a close-up of the envelope and the address of Hillingham Estate is not London: It states that Hillingham is situated in Faversham, Kent, a town located approximately 50 English miles away from London. (00:35:30 - 00:40:05)
Factual error: When Lucy walks through the garden maze at night, her skirt blows up and you can see that she is wearing red modern underwear underneath. This can also be glimpsed in the scene where Dracula first enters her bedroom. Women of the Victorian era wore long loose drawers which extended below the knee. (00:41:40 - 00:58:30)
Factual error: At the cinematograph, Mina says to Dracula, "How can you call this science? Do you think Madame Curie would invite such comparisons? Really!" The movie takes place in year 1897, but Marie Curie's works weren't published until 1898. (00:49:30)
Factual error: When Professor Van Helsing is about to perform the blood transfusion on Lucy, he says, "I've only experimented. Landsteiner's method." However, Karl Landsteiner's method was about the ABO blood types, which Van Helsing knows nothing about (in keeping with the novel, the transfusion is carried out without any mention of compatible blood groups), and the first of Landsteiner's groundbreaking articles about the subject wasn't published until 1900, three years after the movie is set. (00:59:47)
Factual error: When Mina is with Dracula in Dr. Seward's room, you can see that she is wearing modern white underwear beneath her sheer nightgown; this is best seen when he confesses to be Dracula and she is upset about him having killed Lucy. Victorian lingerie consisted of a long chemise and long loose drawers which extended below the knee. (01:37:55)
Answer: It's unlikely they were falling in love with Harker: they are sadistic, baby-eating monsters who regarded Harker as food and a temporary plaything. As for them sleeping in the open, the local populace dreads and avoids Dracula's castle, so there's hardly any fear of intruders. Van Helsing did enter and kill them, but they reckoned, mistakenly, that he too would be too afraid to do so, especially after their horse-mauling escapades the previous night.
Jukka Nurmi