Code Red finally released this DVD and I watched my copy tonight.
This movie and THE HOUSE OF EXORCISM are probably the most blatant EXORCIST rip-offs from the 1970s.
Code Red's DVD release of BEYOND THE DOOR (the uncut 109 minute version) uses the title BEYOND THE DOOR for the box cover and the end credits. However, the opening credits use the UK title THE DEVIL WITHIN HER.
Juliet Mills plays Jessica, a woman who finds out she is pregnant and soon learns that the baby is developing inside her at an unusually rapid rate. Before long, Juliet starts talking in a deep voice, her face becomes ugly, she spews green vomit (quite frequently), and her head spins around. In addition, dresser drawers open and close by themselves and the eyes on her daughter's dolls begin to glow.
There's nothing new or especially interesting in this movie. But if you're a fan of EXORCIST rip-offs, this is one of the more infamous.