[woodbutcher1963]

Reminds me of the Brian De Palma movie(not a porno) from the 1980s “Body Double”.
It was a murder mystery voyeurism flick about a B-list Hollywood actor who gets set up to witness a murder.

The actor is staring in some vampire movie and when he bites into the woman's neck they cut the action and bring in the “body double” who's boobs are larger for the blood to run down her chest.

[Ruy Dias de Bivar]

And she warned them she was about to start her period and her boobs were sore. Saw it way back then. I keep confusing it with Body Heat.