I have no problem with the idea of the glow making them feel happy, even euphoric; it's the idea that it's somehow overriding their decision-making power that I disagree with.
To quote Giles:
“However much Buffy and Angel might love or miss each other— What Buffy’s experiencing right now—is the pull of something far more ancient—something far more powerful—and far more destructive than anyone on this omniverse has ever felt before.”

And again:

Xander: "I wanna know why Angel dressed like a fetish bad guy and became a killer!"
Giles: "I'm not sure 'killer' is the right word. The power that Twilight has on it's subjects-"

Both these lines more than suggest that both Buffy and Angel are under the 'influence' of Twilight, and that the extends beyond the glow.