Elise is supposed to be the be all expert in the paranormal, (Spoilers) she left one of the Red Doors open to allow the demons to influence the Lambert family, specifically the Witch Demon, who has been trying to get Josh and kills Elise in the first film and the Darth Maul Demon, who takes control of his son. Given that Elise is an expert in the paranormal, she should have known that an open doorway would allow Demons into the world to influence humans. That was kind of a break in the character and felt like a bad connection to the first film, it also made Elise look not knowledgeable when she is supposed to be an expert.