Just rewatch the scene where the Master paws and bites Buffy, it's more her reaction than anything else, she's like a pornstar faking it (as indeed she is in Get It Done).
No, she doesn't. It you mean that she sounds orgasmic in either of these scenes... well, no. But in Get It Done
it does look like she's getting sexually assaulted. In Prophecy Girl
(and yes, I rewatched it just now) she looks terrified and has a tear in her eye while the Master is talking ("If you didn't come, I couldn't go") and then when he bites her, she has an expression of pain for less than a second as this is how long it lasts before she loses consciousness.
Those must be some really disturbing porn flicks if this is how their stars are acting before and during sex...
If you want to see a person actually showing signs of sexual pleasure while being bitten, see the William/Drusilla flashback in Fool For Love
As I recall Spike doesn't actually get to bite Buffy in Out of My Mind?
He pins her to the ground and gets his teeth on her neck, but doesn't get to draw blood before his chip works.
As for Dracula it was at least semi-consensual, the point being that this is a matter of seduction, whether we think they just had the biting or actually had sex?
But when "seduction" includes literal hypnotism, is that actually "consensual"? We've seen Drusilla hypnotize Kendra and then kill her because Kendra was so out of it she had no idea what was going on, let alone defend herself. And I believe few people would argue that Kendra consented to being killed.
They definitely didn't have sex, though. I never thought they did, because there's no way that Buffy wouldn't have felt terribly guilty both for cheating on Riley and for sleeping with an evil vampire (if she thought she consented to it) or that she wouldn't have been upset if she had been raped, and that the show would just gloss over it. (Of course you also get a confirmation in Entropy
when she says she only slept with four guys.)
(what I always wonder is what happened between Dracula and Joyce?)
Maybe she served him hot chocolate.
When the show doesn't tell you in any way that a character had sex, especially dubious consent sex, it's always a given that they didn't. Sure, nobody can prove that Joyce wasn't having one-night stands all the time, or that Buffy or Willow or Xander didn't sleep with a bunch of people off-screen (and then lied about it or kept silent about it), but it stands to reason that the show would have let us know somehow, rather than leave us thinking that Buffy, Willow and Xander slept with just 4, 3 and 2 people, respectively, and that Joyce's only love/sex life since moving to Sunnydale was Ted, Band Candy
sex with Giles, and the guy she started dating shortly before her death, which was made a big deal of exactly because Joyce so rarely dated.